Local part
The part of an email address before the @, which only the receiving domain may interpret; RFC 5321 limits it to 64 octets.
What it means
RFC 5321 says the local part must be interpreted and given meaning only by the host named after the @. Sending systems must not change it, and whether dots, case or a +tag make a difference is the receiving provider's choice: for @gmail.com addresses, for example, Gmail ignores dots, while for addresses at a Workspace domain dots do count.
RFC 5322 allows a wider syntax than most people use, including quoted strings with spaces, so overly strict form validation rejects valid addresses. Some local parts have reserved roles (RFC 2142): every domain that receives mail must accept postmaster, and abuse is the conventional address for abuse reports.
Related terms
Sources
What this definition rests on. The wording is ours; the facts are theirs.
- RFC 5321, section 2.3.11: Mailbox and Addressrfc-editor.org
- RFC 5321, section 4.5.3.1.1: Local-partrfc-editor.org
- RFC 5322, section 3.4.1: Addr-Spec Specificationrfc-editor.org
- RFC 2142: Mailbox Names for Common Services, Roles and Functionsrfc-editor.org
- Google, Gmail Help: Dots don't matter in Gmail addressessupport.google.com
All 432 terms in the glossaryThe wiki: blocklists and bounce codes