What makes an email address valid?
Last updated 3 July 2026
Every email address follows the same simple structure — and a handful of rules decide whether it's valid. Here's the anatomy, the rules, and the mistakes that quietly break addresses.
Quick answer: A valid email address islocal-part@domain.tld — a name, exactly one @, and a real domain ending in a top-level domain like .com. The name may contain letters, numbers and . _ % + - but no spaces or doubled dots; the domain needs at least one dot and a valid ending. Want to check a list against these rules? Use the freeemail validator.
The anatomy of an email address
Every address has two parts joined by an @:
- The local part — everything before the
@(e.g.sarah.chen). This identifies the mailbox. - The domain — everything after the
@(e.g.acme.io). It names the mail server, and ends in a top-level domain (TLD) such as.com,.orgor.co.uk.
Rules for the local part (before the @)
- Allowed characters: letters, numbers, and
. _ % + -. - No spaces.
- No dot at the very start or end, and no two dots in a row (
a..bis invalid). - Up to 64 characters long.
So name+newsletter@example.com andfirst.last@example.com are valid, while.name@example.com and na me@example.com are not.
Rules for the domain (after the @)
- Exactly one
@in the whole address. - At least one dot, separating the domain name from its ending.
- A valid TLD of two or more letters (
.com,.io,.co.uk). - No dot or hyphen at the edge of a label, and no doubled dots.
- The whole address is at most 254 characters.
The typos that quietly break addresses
Most "invalid" addresses in a real list aren't exotic — they're small mistakes:
- Wrong ending:
gmail.con,gmail.cm,outlook.co. - Misspelled provider:
gmial.com,hotmial.com,yaho.com. - Missing the dot or the domain entirely:
name@gmailcom,name@. - A stray space or trailing comma copied in from a list.
A good validator catches these and, for likely provider typos, suggests the intended spelling.
Format validation vs. mailbox verification
This is the key distinction. Format validation checks that an address follows the rules above — it's instant, private, and catches the large majority of bad addresses. Mailbox verification goes further and asks the mail server whether the address actually exists, which requires sending your list to a third-party service.
For most list cleanup, format validation is enough and keeps your data private. You can validate a whole list in your browser, then clean it to also remove duplicates and role accounts before importing.
Frequently asked questions
What is a valid email address format?
A valid address has a local part (the name before the @), a single @ symbol, and a domain with at least one dot and a valid ending — for example name@example.com. The local part can contain letters, numbers and some symbols but no spaces or misplaced dots, and the domain must be a real hostname ending in a top-level domain like .com or .co.uk.
Is a plus sign (+) allowed in an email address?
Yes. Characters like + . _ % and - are allowed in the local part, so addresses such as name+newsletter@example.com are valid. Many people use the + to create filterable aliases.
Can an email address have two @ symbols?
No. A valid address has exactly one @ separating the local part from the domain. More than one @ makes it invalid.
Does a valid format mean the email actually works?
No. Format validation only confirms the address is well-formed. It can't tell you whether the mailbox exists or can receive mail — that requires contacting the mail server. Format checking still removes the large majority of bad addresses (typos and malformed entries) and can be done privately in your browser.
Why is gmail.con flagged even though it looks valid?
Because .con isn't a real ending and it's an extremely common typo for .com. A good validator flags likely domain typos (gmail.con → gmail.com, gmial.com → gmail.com) even when the address is technically well-formed.