Postmaster address
The reserved postmaster mailbox that every domain receiving mail must accept (RFC 5321), so that problems with its mail system can always be reported.
What it means
RFC 5321 requires any SMTP server that delivers or relays mail for a domain to accept mail to postmaster at that domain, without regard to case, and even the bare RCPT TO:<Postmaster>. Servers are expected to make every reasonable effort to accept mail to it, blocking it only in extreme cases such as an attack, and then narrowly. RFC 2142 lists postmaster as the address for SMTP matters, alongside abuse for abuse reports and hostmaster for DNS.
For senders, the postmaster address is how to reach a receiving organisation's mail administrators when their system rejects legitimate mail. For domain owners, it should be delivered to someone who reads it.
Related terms
Sources
What this definition rests on. The wording is ours; the facts are theirs.
- RFC 5321, section 4.5.1: Minimum Implementationrfc-editor.org
- RFC 2142: Mailbox Names for Common Services, Roles and Functionsrfc-editor.org
All 432 terms in the glossaryThe wiki: blocklists and bounce codes