mailaddr(7)

💌 mailaddr(7) — like, the whole vibe of mail addressing

okay bestie, so you know how the manual is called mailaddr(7)? it lives in the Miscellaneous Information Manual section, and it's genuinely just a little intro tour of how email addresses work. no cap, it's giving "welcome to the internet, here's your name tag." 🎀

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✨ NAME ✨

mailaddr — mail addressing description 💖

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🌸 DESCRIPTION 🌸

So this page is a lil' crash course on SMTP mail addresses, the kind we use on the Internet. They go like this, general format:

user@domain

where a domain is a hierarchical, dot-separated list of subdomains. and the way that all three of these are literally the same address... iconic:

john.doe@monet.example.com
John Doe <john.doe@monet.example.com>
john.doe@monet.example.com (John Doe)

The domain part (that's monet.example.com btw) is a mail-accepting domain. it can be a host, and back in the day it usually was, but lowkey it doesn't have to be. also the domain part is not case sensitive, so type it however your heart desires. 🦋

The local part (that's john.doe) is often a username, but honestly its meaning is defined by the local software. sometimes it's case sensitive — although that's unusual. and if you see a local part that looks like straight-up garbage? 💀 usually that's because of a gateway between an internal e-mail system and the net. here are the examples:

"surname/admd=telemail/c=us/o=hp/prmd=hp"@some.where
USER%SOMETHING@some.where
machine!machine!name@some.where
I2461572@some.where

and in order, those are: an X.400 gateway, a gateway to an arbitrary internal mail system that lacks proper internet support, a UUCP gateway, and the last one is just boring username policy. 🙈 (not everything can be main character energy, bestie.)

The real-name part (John Doe) can go either before the <>, or in () at the end. (strictly speaking the two aren't the same, but that difference is beyond the scope of this page — iykyk.) and the name may have to be quoted using "", for example if it contains a ".":

"John Q. Doe" <john.doe@monet.example.com>

🎀 Abbreviation 🎀

Some mail systems let users abbreviate the domain name. for instance, users at example.com may get away with "john.doe@monet" to send mail to John Doe.

⚠️ bestie. this behavior is deprecated. sometimes it works, but you should NOT depend on it. periodt.

🛣️ Route-addrs 🛣️

In the past, sometimes one had to route a message through several hosts to get it to its final destination. addresses which show these relays are termed "route-addrs". they use this syntax:

<@hosta,@hostb:user@hostc>

this specifies that the message should be sent to hosta, from there to hostb, and finally to hostc. many hosts disregard route-addrs and just send directly to hostc — rude but valid. 💅

Route-addrs are very unusual now. they occur sometimes in old mail archives. it's generally possible to ignore all but the "user@hostc" part of the address to determine the actual address. so like, the drama of the middle hosts? skip it. 🫶

👑 Postmaster 👑

Every site is required to have a user or user alias designated "postmaster" to which problems with the mail system may be addressed. the "postmaster" address is not case sensitive. she's always available, she's always listening. 🌈

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🍓 FILES 🍓

• /etc/aliases
• ~/.forward

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💜 SEE ALSO 💜

• mail(1)
• aliases(5)
• forward(5)
• sendmail(8)
• IETF RFC 5322

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okay that's the whole page, bestie!! go forth and address your mail correctly. slay. 💅✨

this was brought to you by the 4.2 Berkeley Distribution, dated 2026-02-08 — yes that's the same page number as the manual, mailaddr(7), we love a full-circle moment. 🦋💖