> Enrich.chat gives AI agents verified work emails and mobiles. To use it from an agent, read https://enrich.chat/agents.md . This is the Markdown version of https://enrich.chat/blog/email-address-formats/

# Email address formats: the rules, the 12 business patterns, and how to choose one

What the standards allow in an address, the patterns companies build from names, how they handle duplicate, hyphenated and accented names, and how to find one company's format.

By Enrich.chat Editorial. Updated October 15, 2026.

**Short answer:** An email address has the format local-part@domain, as in jane.doe@acme.com. [RFC 5321](https://www.rfc-editor.org/rfc/rfc5321.html#section-4.5.3.1) caps the local part at 64 octets and the domain at 255, and the whole address works out to 254 characters. Companies build the local part from names in a fixed pattern, such as first.last (jane.doe@), first initial plus last name (jdoe@) or first name only (jane@).

## Key takeaways

- An email address is local-part@domain. [RFC 5321](https://www.rfc-editor.org/rfc/rfc5321.html#section-4.5.3.1) allows 64 octets before the @ and 255 after it, and a [verified erratum](https://errata.rfc-editor.org/eid1690) puts the whole address at 254 characters, not 320.
- The standard lets a server treat the local part as case-sensitive, but [Google Workspace](https://knowledge.workspace.google.com/admin/users/name-guidelines-for-users-and-groups) converts every username to lowercase. Treat Jane.Doe@ and jane.doe@ as the same address.
- The common business patterns are first.last, first initial plus last name, and first name only. Microsoft Exchange builds them from [templates](https://learn.microsoft.com/en-us/exchange/email-addresses-and-address-books/email-address-policies/email-address-policies) such as %g.%s for jane.doe@.
- Duplicate names get a middle initial or a number. [Washington State's naming standard](https://watech.wa.gov/sites/default/files/2025-06/EA-01-04-S%20Email%20Address%20Naming%20Standard.pdf) gives Person.Smith1@ and Person.A.Smith@ as examples.
- Role addresses have a standard too. [RFC 2142](https://www.rfc-editor.org/rfc/rfc2142.html) defines postmaster@, abuse@, sales@, support@ and others, and every mail server must accept postmaster@.

## What is the format of an email address?

Every email address has the format local-part@domain. In jane.doe@acme.com, the local part is jane.doe, which names the mailbox. The domain is acme.com, which names the organization that receives the mail. [RFC 5322](https://www.rfc-editor.org/rfc/rfc5322.html#section-3.4.1), the internet standard for message format, calls this an addr-spec.

In an email header, the address often travels with a display name, as in Jane Doe \<jane.doe@acme.com>. RFC 5322 calls that form a [name-addr](https://www.rfc-editor.org/rfc/rfc5322.html#section-3.4). The display name is a label for people. Mail servers only route on the part inside the angle brackets.

**Figure 1: The parts of an email address and their limits.** The header form Jane Doe, then jane.doe+invoices@eu.acme.com in angle brackets, with each part labelled. The display name sits outside the brackets. The local part, jane.doe+invoices, can be up to 64 octets and ends in a plus tag. The domain, eu.acme.com, can be up to 255 octets, and each label such as acme up to 63. The whole address can be up to 254 characters, not 320, because the SMTP path limit of 256 octets includes the angle brackets. Three panels list the characters allowed in the local part and the domain, and the case rules.

*The parts of an email address and the limits the standards set. Sources: lengths from [RFC 5321](https://www.rfc-editor.org/rfc/rfc5321.html#section-4.5.3.1) and [RFC 1035](https://www.rfc-editor.org/rfc/rfc1035.html#section-2.3.4), the 254 limit from [erratum 1690](https://errata.rfc-editor.org/eid1690), characters from [RFC 5322](https://www.rfc-editor.org/rfc/rfc5322.html#section-3.2.3), and the lowercase rule from [Google Workspace](https://knowledge.workspace.google.com/admin/users/name-guidelines-for-users-and-groups).*

A good example of a business email address is short, lowercase, and built from the person's name at the company's own domain, like jane.doe@acme.com. A free webmail address such as jane.doe@gmail.com works for personal mail, but it does not tell the reader where the sender works.

### How long can an email address be?

An email address can be up to 254 characters long. The local part can be up to 64 octets and the domain up to 255, under [section 4.5.3.1 of RFC 5321](https://www.rfc-editor.org/rfc/rfc5321.html#section-4.5.3.1), the SMTP standard. Each label between the dots of a domain is capped at 63 octets by [RFC 1035](https://www.rfc-editor.org/rfc/rfc1035.html#section-2.3.4). An octet is one byte, which is one character in plain ASCII.

Some guides quote 320 characters: 64, plus 1 for the @, plus 255. That sum appeared in [RFC 3696](https://www.rfc-editor.org/rfc/rfc3696.html#section-3) in 2004. But RFC 5321 also caps the whole path at 256 octets, and the path includes the angle brackets around the address. A [verified erratum to RFC 3696](https://errata.rfc-editor.org/eid1690) does the math and concludes that the upper limit "should normally be considered to be 254." [Microsoft 365](https://learn.microsoft.com/en-us/entra/identity/authentication/concept-sspr-policy) is stricter still: its user names allow 48 characters after the @ and 113 in total.

## What characters are allowed in an email address?

The standards allow far more characters than mail platforms do. Under [RFC 5322](https://www.rfc-editor.org/rfc/rfc5322.html#section-3.2.3), a local part can use letters, digits and these symbols: ``! # $ % & ' * + - / = ? ^ _ ` { | } ~``. Dots can sit between characters, but not first, last or twice in a row. The domain is stricter. [RFC 5321](https://www.rfc-editor.org/rfc/rfc5321.html#section-4.1.2) allows only letters, digits and hyphens in each label, and a label must start and end with a letter or digit.

Quotes stretch the rules further. "jane doe"@acme.com, with a space inside quotes, is valid syntax. RFC 5321 still tells receiving hosts to avoid mailboxes that need quotes or that depend on case. In practice, business platforms do not issue them.

Google Workspace and Microsoft 365 each allow a much smaller set. The table compares the standard with both, from [Google's name guidelines](https://knowledge.workspace.google.com/admin/users/name-guidelines-for-users-and-groups) and [Microsoft's username policy](https://learn.microsoft.com/en-us/entra/identity/authentication/concept-sspr-policy), checked on October 15, 2026.

*Address rules in the standard and on the two largest business mail platforms, checked October 15, 2026.*

| Rule | RFC 5321 and 5322 | Google Workspace username | Microsoft 365 user name |
| --- | --- | --- | --- |
| Length before the @ | 64 octets | 64 characters, or 100 for an alias | 64 characters |
| Length after the @ | 255 octets | Not stated | 48 characters, 113 in total |
| Symbols allowed | ``! # $ % & ' * + - / = ? ^ _ ` { \| } ~`` and dots | Dashes, underscores, apostrophes, periods | `' . - _ ! # ^ ~` |
| Plus sign | Allowed | Not allowed in a username | Not in user names, but on by default as a plus-address tag |
| Capital letters | Allowed, and the local part may be case-sensitive | Converted to lowercase | Allowed (A to Z) |
| Accented letters | Only with the SMTPUTF8 extension | Restricted | Not allowed (A to Z only) |
| Dots | Not first, last or doubled | Not first, last or doubled | Not right before the @ |

The plus sign has a special job. In Exchange Online, [plus addressing is on by default](https://learn.microsoft.com/en-us/exchange/recipients-in-exchange-online/plus-addressing-in-exchange-online): mail to sean+newsletter@contoso.com goes to sean@contoso.com. People use the tag to sort mail, so a plus sign in an address you collect usually means a tag, not a different person.

### Are email addresses case sensitive?

The domain is not. The local part can be under the standard, but the standard itself warns against relying on it. [Section 2.4 of RFC 5321](https://www.rfc-editor.org/rfc/rfc5321.html#section-2.4) says the local part "MUST BE treated as case sensitive," so a server may treat Smith and smith as two users. The same section says exploiting that "impedes interoperability and is discouraged." Domains follow DNS rules, so ACME.com and acme.com are the same.

Mail platforms settle it. [Google Workspace](https://knowledge.workspace.google.com/admin/users/name-guidelines-for-users-and-groups) converts any capital letters in a new username to lowercase. Write addresses in lowercase, and treat Jane.Doe@ and jane.doe@ as one person when you clean a list.

Dots are a separate trap. On gmail.com, [dots don't matter](https://support.google.com/mail/answer/7436150?hl=en), so jane.doe@gmail.com and janedoe@gmail.com reach the same inbox. Google says that does not hold for Gmail used through work or school, where dots change the address. Never drop the dots from a business address.

### Can an email address use accents or other alphabets?

Yes, under newer standards, but support is patchy, so business addresses rarely use them. [RFC 6531](https://www.rfc-editor.org/rfc/rfc6531.html#section-3.2), published in 2012, adds an SMTP extension called SMTPUTF8 that carries addresses like josé@ in UTF-8. If the next server does not offer the extension, the sending server must not pass the address on. Gmail began to [recognize accented and non-Latin addresses](https://blog.google/products-and-platforms/products/gmail/a-first-step-toward-more-global-email/) on August 5, 2014, and Google noted that every provider and every website must adopt the standard for it to work.

## What are the most common business email formats?

Business addresses are built from the person's name in a handful of patterns. The three you will meet most are first.last (jane.doe@), first initial plus last name (jdoe@) and first name only (jane@). In [Interseller's 2019 study of more than five million companies](https://www.interseller.io/blog/2019/02/04/top-email-address-patterns-by-company-size/), jane@ led at firms with up to 50 staff, jdoe@ from 51 to 1,000, and jane.doe@ above 1,000, a split the [email permutator](https://enrich.chat/tools/email-permutator/) charts by headcount.

The table lists twelve patterns for Jane M. Doe at acme.com. The third column shows the Microsoft Exchange template that builds each one. In those templates, %g is the first name, %s the last name, %i the middle initial, and %1g the first letter of the first name, according to [Microsoft's address policy documentation](https://learn.microsoft.com/en-us/exchange/email-addresses-and-address-books/email-address-policies/email-address-policies).

| Pattern | Jane M. Doe at acme.com | Exchange template | Watch for |
| --- | --- | --- | --- |
| first.last | jane.doe@acme.com | `%g.%s` | Clashes only on the same full name |
| flast (first initial, last name) | jdoe@acme.com | `%1g%s` | John Doe gets the same address |
| first | jane@acme.com | `%g` | Breaks at the second Jane |
| firstlast | janedoe@acme.com | `%g%s` | Harder to read at a glance |
| f.last | j.doe@acme.com | `%1g.%s` | Same clashes as flast |
| first_last | jane_doe@acme.com | `%g_%s` | Easy to mistype as a dot |
| firstl (first name, last initial) | janed@acme.com | `%g%1s` | Jane Dunn gets the same address |
| first.l | jane.d@acme.com | `%g.%1s` | Same clashes as firstl |
| last.first | doe.jane@acme.com | `%s.%g` | Suits surname-first naming |
| lastf | doej@acme.com | `%s%1g` | John Doe gets the same address |
| first-last | jane-doe@acme.com | `%g-%s` | Blurs with hyphenated surnames |
| first.m.last | jane.m.doe@acme.com | `%g.%i.%s` | Often used to break ties |

The Exchange admin center offers six ready-made name formats: first.last, flast, firstl, last.first and lastf from the table, plus lfirst, which turns Jane Doe into djane@. Every other pattern in the table takes a custom template.

## How do companies set and enforce an email format?

An admin picks a pattern once, and the mail system applies it to each new account. Microsoft Exchange does this with email address policies. Google Workspace offers no address template, so the admin types each username or imports names from a file or a directory.

### Microsoft Exchange and Microsoft 365

In Exchange Server, an [email address policy](https://learn.microsoft.com/en-us/exchange/email-addresses-and-address-books/email-address-policies/email-address-policies) has three parts: an address template such as %g.%s@contoso.com, a recipient filter, and a priority. Filters can pick recipients by company, department, state or custom attribute. So one organization can give staff first.last and give a subsidiary a different rule. Exchange checks policies in priority order, and the first match wins. A default policy covers everyone left over, and an admin can exempt one person by switching off policy updates on their mailbox.

Exchange Online works differently. Microsoft's reference says that [in Exchange Online, email address policies are available only for Microsoft 365 Groups](https://learn.microsoft.com/en-us/powershell/module/exchange/new-emailaddresspolicy?view=exchange-ps). A cloud user's primary address is usually the one the admin typed when creating the account, according to [Microsoft's alias guide](https://learn.microsoft.com/en-us/microsoft-365/admin/email/add-another-email-alias-for-a-user?view=o365-worldwide). Companies that sync from Active Directory carry their old pattern over, because Microsoft Entra ID copies the on-premises user name by default, per [Microsoft's username policy](https://learn.microsoft.com/en-us/entra/identity/authentication/concept-sspr-policy).

### Google Workspace

Google Workspace leaves the pattern to the admin. Its [options for adding users](https://knowledge.workspace.google.com/admin/users/options-for-adding-users) are one at a time, up to 10 at once, a CSV file of up to 150,000 users, Google Cloud Directory Sync from an LDAP directory, or the Directory API. The one-at-a-time form flags a username that already belongs to an account. Whatever names the CSV file or directory holds become the format.

### Written naming standards

Large organizations write the rule down. Washington State's [Email Address Naming Standard](https://watech.wa.gov/policies/email-address-naming-standard-0), EA-01-04-S, adopted December 10, 2024, requires state agencies to use FirstName.LastName@agency.wa.gov or FirstName.mi.LastName@agency.wa.gov. The sign-in name must match the primary address. Plus addressing, such as first.last+billing@, is allowed. A written rule like this settles the hard cases before they reach the help desk.

Aliases let a company keep one format and still catch variations. [Google Workspace](https://knowledge.workspace.google.com/admin/users/add-or-delete-an-alternate-email-address-email-alias) allows up to 30 aliases per user, and [Microsoft 365](https://learn.microsoft.com/en-us/microsoft-365/admin/email/add-another-email-alias-for-a-user?view=o365-worldwide) allows up to 400.

## How do email formats handle duplicate, hyphenated and accented names?

Every format needs a rule for names that do not fit, and the rule changes the address. The figure shows how three common formats treat five hard cases, using rules from published naming standards and vendor documentation.

**Figure 2: How three formats handle hard names.** A grid shows how first.last, first initial plus last name, and first name only handle five hard names. A second Jane Doe becomes jane.doe2, jdoe2 or jane2, or gets a middle initial. Mary-Kate O'Brien becomes mary-kate.obrien, mobrien or mary-kate, with the apostrophe dropped. José Peña becomes jose.pena, jpena or jose. Mary Ann Lee becomes maryann.lee or mary_ann.lee, mlee or maryann. Anne Wallace, now Anne Jones, becomes anne.jones or ajones, with the old address kept as an alias, while first name only stays anne.

*How first.last, flast and first-name-only formats handle hard names. Orange marks what the rule adds. Names are illustrative. Sources: duplicate and hyphen rules from [Washington State's naming standard](https://watech.wa.gov/sites/default/files/2025-06/EA-01-04-S%20Email%20Address%20Naming%20Standard.pdf), the apostrophe rule from [UW-Madison](https://kb.wisc.edu/ghi/page.php?id=33352), the underscore from [Microsoft](https://learn.microsoft.com/en-us/troubleshoot/microsoft-365/admin/active-directory/email-address-contain-underscore), and old addresses kept as aliases from [Google Workspace](https://knowledge.workspace.google.com/admin/users/change-a-users-email-address).*

### Duplicate names

Two people cannot share one address, so the second person with a name gets a middle initial or a number. [Washington State's standard](https://watech.wa.gov/sites/default/files/2025-06/EA-01-04-S%20Email%20Address%20Naming%20Standard.pdf) allows both: Person.Smith1@ and Person.Smith2@, or Person.A.Smith@ and Person.B.Smith@. The shorter the format, the sooner this happens. Under first name only, any second Jane needs a tie-breaker. Under first.last, only a second Jane Doe does.

### Hyphens, apostrophes and spaces

In the naming standards we checked, hyphens stay and apostrophes go. [Washington State](https://watech.wa.gov/sites/default/files/2025-06/EA-01-04-S%20Email%20Address%20Naming%20Standard.pdf) accepts both Person.SmithJones@ and Person.Smith-Jones@ for a double surname. The University of Wisconsin-Madison allows only letters, numbers, periods and hyphens in its [first.last addresses](https://kb.wisc.edu/ghi/page.php?id=33352), and says no other characters, "including apostrophes," will be accepted. So O'Brien becomes obrien.

Spaces need care in Microsoft 365. If an on-premises address contains a space, Microsoft Entra Connect [replaces it with an underscore](https://learn.microsoft.com/en-us/troubleshoot/microsoft-365/admin/active-directory/email-address-contain-underscore) when it syncs. That is how Mary Ann can turn into mary_ann.

### Accented letters

Plain-ASCII rules push the accents out, so José Peña usually becomes jose.pena. [Microsoft 365 user names](https://learn.microsoft.com/en-us/entra/identity/authentication/concept-sspr-policy) accept only the letters A to Z, and an address with é can only travel between servers that support [SMTPUTF8](https://www.rfc-editor.org/rfc/rfc6531.html#section-3.2). The accents can stay in the display name. [Google Workspace](https://knowledge.workspace.google.com/admin/users/name-guidelines-for-users-and-groups) accepts any UTF-8 characters in first and last names, which appear next to the address in the inbox.

### Name changes and nicknames

When someone changes their name, the admin changes the address and keeps the old one as an alias. In Google Workspace, the old address [automatically becomes an email alias](https://knowledge.workspace.google.com/admin/users/change-a-users-email-address), so mail still arrives, but the person must sign in with the new one. Microsoft's own [rename example](https://learn.microsoft.com/en-us/microsoft-365/admin/add-users/change-a-user-name-and-email-address?view=o365-worldwide) moves anne.wallace@contoso.com to anne.jones@contoso.com.

Nicknames work the same way. [Microsoft's alias guide](https://learn.microsoft.com/en-us/microsoft-365/admin/email/add-another-email-alias-for-a-user?view=o365-worldwide) gives Jenna a second address, jen@, because some people call her Jen. [Washington State](https://watech.wa.gov/sites/default/files/2025-06/EA-01-04-S%20Email%20Address%20Naming%20Standard.pdf) also lets staff use the preferred name they are commonly known by, including a single name or a surname that comes first.

## What are role-based email addresses like postmaster@ and abuse@?

A role-based address belongs to a job, not a person, so it keeps working when staff change. That gives business email two types of address: personal ones like jane.doe@ and role ones like sales@. [RFC 2142](https://www.rfc-editor.org/rfc/rfc2142.html), from 1997, lists the standard role names. It asks every organization to support each name whose function it has, and says the names must work in any case, so POSTMASTER@ and postmaster@ reach the same mailbox.

*Role mailbox names defined in [RFC 2142](https://www.rfc-editor.org/rfc/rfc2142.html). RFC 5321 also makes postmaster@ mandatory.*

| Mailbox | What it is for |
| --- | --- |
| postmaster@ | Mail delivery problems. Required on every server that delivers mail |
| abuse@ | Reports of spam and other abuse |
| security@ | Security bulletins and questions |
| noc@ | Network operations |
| hostmaster@ | DNS problems |
| webmaster@ or www@ | Website problems |
| info@ | General information about the organization |
| sales@ | Product purchase questions |
| support@ | Problems with a product or service |
| marketing@ | Product marketing |
| list-request@ | Join and leave requests for a mailing list at list@ |

Postmaster is the one a mail server cannot skip. [RFC 5321](https://www.rfc-editor.org/rfc/rfc5321.html#section-4.5.1) says any system that relays or delivers mail must support postmaster as a case-insensitive name. [Google Workspace](https://knowledge.workspace.google.com/admin/users/name-guidelines-for-users-and-groups) treats abuse and postmaster as reserved words that no username or alias can take.

Companies also run team inboxes that no RFC defines, such as billing@, press@, careers@ or hello@. When several people should answer mail sent to info@ or sales@, Microsoft recommends a [shared mailbox](https://learn.microsoft.com/en-us/microsoft-365/admin/email/add-another-email-alias-for-a-user?view=o365-worldwide) instead of an alias on one person's account. Role addresses tell you nothing about how a company spells names, so skip them when you work out its pattern.

## How do you choose a professional email format for your company?

Choose first.last unless you are sure the company will stay small. It reads as a name, it clashes least, and it rarely needs to change as you grow. Then write down the rules for hard names before the first one arrives.

**Figure 3: Which colleagues share an address with a new Jane Doe.** A new hire named Jane Doe joins a company where Jane Smith, John Doe, Jane Dunn and another Jane Doe already work. Under first name only, her address jane@ clashes with three colleagues. Under first initial plus last name, jdoe@ clashes with two. Under first name plus last initial, janed@ clashes with two. Under first.last, jane.doe@ clashes only with the other Jane Doe.

*The shorter the format, the more colleagues share an address. Only an identical full name breaks first.last, which is why naming standards such as [Washington State's](https://watech.wa.gov/policies/email-address-naming-standard-0) add a middle initial or a number. Names are illustrative.*

| Format | Good for | Watch out for |
| --- | --- | --- |
| first.last (jane.doe@) | Any size of company. Easy to read and to guess | Very long names may need shortening to fit 64 characters |
| flast (jdoe@) | Short addresses at a mid-sized firm | Clashes when two people share a first initial and surname |
| firstl (janed@) | Small teams that use first names | Clashes when two people share a first name and last initial |
| first (jane@) | A small team that will stay small | Breaks at the second person with the same first name |

Once you pick a format, these steps keep it consistent:

1. **Apply it to everyone.** Include founders and executives. Mixed formats make your own staff harder to reach.
2. **Write a duplicate rule.** Add a middle initial first, then a number, the way [Washington State](https://watech.wa.gov/policies/email-address-naming-standard-0) does.
3. **Normalize names the same way every time.** Use lowercase, drop accents, apostrophes and spaces, and decide once whether hyphens stay.
4. **Match the sign-in name to the address.** Microsoft calls it a [best practice](https://learn.microsoft.com/en-us/microsoft-365/admin/add-users/change-a-user-name-and-email-address?view=o365-worldwide), and Washington State requires it.
5. **Use aliases for variations.** If you move from jane@ to jane.doe@, keep the old address as an alias so mail keeps arriving.
6. **Create role addresses before you publish any.** Set up postmaster@ and abuse@ for the mail system, and info@, sales@ and support@ for customers. Publish those on your website instead of personal addresses.

## How do you find a specific company's email format?

Find one real address at the company and match it to the person's name, or look the domain up in a format finder. Then verify the address you build before you send to it.

1. **Look up the domain.** The free [email format finder](https://enrich.chat/tools/email-format-finder/) shows a domain's most common pattern, an example address, other patterns seen there, and whether the domain is catch-all. Each check uses one of 10 free lookups shared across the website tools.
2. **Browse company pages.** The [company email format directory](https://enrich.chat/email-format/) has pages for individual companies, such as the [Goldman Sachs email format](https://enrich.chat/email-format/goldman-sachs/), [Deloitte email format](https://enrich.chat/email-format/deloitte/), [Microsoft email format](https://enrich.chat/email-format/microsoft/), [JPMorgan Chase email format](https://enrich.chat/email-format/jpmorgan-chase/) and [Accenture email format](https://enrich.chat/email-format/accenture/).
3. **Find one public address.** Press releases, author bylines and conference speaker pages often show a staff address. Skip role addresses like press@, since they show the domain but not the pattern.
4. **List the options if you are unsure.** The [email permutator](https://enrich.chat/tools/email-permutator/) lists every likely address for a name, right in your browser.
5. **Verify before you send.** The [email finder](https://enrich.chat/tools/email-finder/) returns the work email on file and labels it verified, catch-all or unknown. If a domain accepts every address, the [catch-all checker](https://enrich.chat/tools/catch-all-checker/) will say so, and the format becomes your main evidence.

Our guide on [how to find anyone's work email](https://enrich.chat/blog/how-to-find-someones-email/) covers methods beyond the format, and the [LinkedIn email finder](https://enrich.chat/tools/linkedin-email-finder/) skips the format step when you have a profile URL. For a list of names, your AI agent can do the lookups through the [Enrich.chat API for agents](https://enrich.chat/agents/). It gets 10 free lookups a day with no signup. After that, a work email found uses 10 credits and a lookup that finds nothing uses 0, so 500 verified emails use 5,000 credits, which fits the Growth plan at $29 a month. See [pricing](https://enrich.chat/pricing/) for every plan.

```text
Use www.enrich.chat to find the verified work email for each person in this list of names and company domains. Show the status of each email, and flag catch-all domains as risky.
```

## Frequently asked questions

### What is the correct format for an email address?

The correct format is local-part@domain, as in jane.doe@acme.com. The local part names the mailbox. It can be up to 64 characters of letters, digits, dots and some symbols, with no spaces. The domain names the organization and uses letters, digits, hyphens and dots, up to 255 characters. The whole address can be up to 254 characters, per [RFC 5321](https://www.rfc-editor.org/rfc/rfc5321.html#section-4.5.3.1). In a header it often appears with a name, as Jane Doe \<jane.doe@acme.com>.

### What is the most common business email format?

Three patterns lead in business email: first.last (jane.doe@acme.com), first initial plus last name (jdoe@acme.com) and first name only (jane@acme.com). Which one a company picks tends to follow its size, and the [email permutator](https://enrich.chat/tools/email-permutator/) charts a 2019 study of formats by headcount. To know one company's format for sure, find one real address there, or enter its domain in the free [email format finder](https://enrich.chat/tools/email-format-finder/).

### Are email addresses case sensitive?

The domain never is. The local part can be in theory: [RFC 5321](https://www.rfc-editor.org/rfc/rfc5321.html#section-2.4) says servers must preserve its case, so Smith and smith could be two users. The same standard says relying on that is discouraged, and major platforms do not. [Google Workspace](https://knowledge.workspace.google.com/admin/users/name-guidelines-for-users-and-groups) converts usernames to lowercase. Write addresses in lowercase and treat case variations as the same address.

### Can an email address have a hyphen, underscore or apostrophe?

Yes. The standard allows all three in the local part, and so do [Google Workspace](https://knowledge.workspace.google.com/admin/users/name-guidelines-for-users-and-groups) and [Microsoft 365](https://learn.microsoft.com/en-us/entra/identity/authentication/concept-sspr-policy) user names. Many employers still drop apostrophes. [UW-Madison](https://kb.wisc.edu/ghi/page.php?id=33352) accepts only letters, numbers, periods and hyphens, so O'Brien becomes obrien. In the domain, hyphens are allowed inside a label but not at its start or end.

### What is a professional email address format?

A professional email address uses your real name at your company's own domain, in lowercase, with no nicknames or numbers unless a number breaks a tie. first.last@company.com is the safest choice because it reads as a name and rarely clashes. Small teams often use first@company.com, but it breaks at the second person with the same first name. Whatever you pick, add aliases for common variations and keep role addresses like sales@ for shared inboxes.

### How do I find out a company's email format?

Find one real address at the company, such as a named contact on a press release, and match it to the person's name. You can also enter the domain in the free [email format finder](https://enrich.chat/tools/email-format-finder/), which shows the most common pattern and whether the domain is catch-all, or browse the [company email format directory](https://enrich.chat/email-format/). Then check the address you build with the [email finder](https://enrich.chat/tools/email-finder/) before you send anything.

## Sources

1. [RFC 5321: Simple Mail Transfer Protocol](https://www.rfc-editor.org/rfc/rfc5321.html)
2. [RFC 5322: Internet Message Format](https://www.rfc-editor.org/rfc/rfc5322.html)
3. [Erratum 1690 to RFC 3696 (maximum address length)](https://errata.rfc-editor.org/eid1690)
4. [RFC 3696: Application Techniques for Checking and Transformation of Names](https://www.rfc-editor.org/rfc/rfc3696.html)
5. [RFC 1035: Domain Names, Implementation and Specification](https://www.rfc-editor.org/rfc/rfc1035.html)
6. [RFC 2142: Mailbox Names for Common Services, Roles and Functions](https://www.rfc-editor.org/rfc/rfc2142.html)
7. [RFC 6531: SMTP Extension for Internationalized Email](https://www.rfc-editor.org/rfc/rfc6531.html)
8. [Email address policies in Exchange Server](https://learn.microsoft.com/en-us/exchange/email-addresses-and-address-books/email-address-policies/email-address-policies)
9. [New-EmailAddressPolicy](https://learn.microsoft.com/en-us/powershell/module/exchange/new-emailaddresspolicy?view=exchange-ps)
10. [Self-service password reset policies: username policies](https://learn.microsoft.com/en-us/entra/identity/authentication/concept-sspr-policy)
11. [Add another email alias for a user](https://learn.microsoft.com/en-us/microsoft-365/admin/email/add-another-email-alias-for-a-user?view=o365-worldwide)
12. [Change a user name and email address](https://learn.microsoft.com/en-us/microsoft-365/admin/add-users/change-a-user-name-and-email-address?view=o365-worldwide)
13. [Microsoft 365 email address contains underscore character](https://learn.microsoft.com/en-us/troubleshoot/microsoft-365/admin/active-directory/email-address-contain-underscore)
14. [Plus addressing in Exchange Online](https://learn.microsoft.com/en-us/exchange/recipients-in-exchange-online/plus-addressing-in-exchange-online)
15. [Name guidelines for users and groups](https://knowledge.workspace.google.com/admin/users/name-guidelines-for-users-and-groups)
16. [Add or delete an alternate email address (email alias)](https://knowledge.workspace.google.com/admin/users/add-or-delete-an-alternate-email-address-email-alias)
17. [Change a user's email address](https://knowledge.workspace.google.com/admin/users/change-a-users-email-address)
18. [Options for adding users](https://knowledge.workspace.google.com/admin/users/options-for-adding-users)
19. [Dots don't matter in Gmail addresses](https://support.google.com/mail/answer/7436150?hl=en)
20. [A first step toward more global email](https://blog.google/products-and-platforms/products/gmail/a-first-step-toward-more-global-email/)
21. [Email Address Naming Standard (EA-01-04-S)](https://watech.wa.gov/policies/email-address-naming-standard-0)
22. [EA-01-04-S Email Address Naming Standard (full text, PDF)](https://watech.wa.gov/sites/default/files/2025-06/EA-01-04-S%20Email%20Address%20Naming%20Standard.pdf)
23. [Microsoft 365: How will firstname.lastname@wisc.edu email addresses be assigned?](https://kb.wisc.edu/ghi/page.php?id=33352)
24. [Top Email Address Patterns By Company Size](https://www.interseller.io/blog/2019/02/04/top-email-address-patterns-by-company-size/)

## Try this prompt

Get the real address, not the pattern

```text
Use www.enrich.chat to find the verified work email for [name] at [company domain], and tell me if the domain is catch-all
```

## Related

- [Email format finder](https://enrich.chat/tools/email-format-finder/)
- [Email permutator](https://enrich.chat/tools/email-permutator/)
- [How to find anyone's work email](https://enrich.chat/blog/how-to-find-someones-email/)