Mail server
A computer running software that sends, receives or stores email: a submission server, an MTA relaying mail, an MX host receiving it, or a mailbox server.
What it means
The phrase covers several roles that may share one machine or be spread over many: the submission server that takes mail from users, the outbound MTA that delivers it, the inbound MX host that receives mail for a domain, and the mailbox server where messages are stored and read. In SMTP the side that connects is the client and the side that accepts is the server, so an MTA relaying mail acts as both.
When a bounce or a blocklist report names your mail server, it means the host whose IP made the SMTP connection: its IP reputation, reverse DNS, HELO name and TLS were what the receiver judged. For senders using a platform, that is the platform's server, not the computer the message was written on.
Related terms
Sources
What this definition rests on. The wording is ours; the facts are theirs.
- RFC 5321, section 2.3.2: Senders and Receiversrfc-editor.org
- RFC 5321, section 2.3.10: Originator, Delivery, Relay, and Gateway Systemsrfc-editor.org
- RFC 5598, section 4: Services and Standardsrfc-editor.org
All 432 terms in the glossaryThe wiki: blocklists and bounce codes