Mail Aliases

The sendmail utility uses the name service aliases map to expand a mail alias into a fully specified address. If mail is sent to a username, but that name cannot be found in the aliases database, the mail is delivered to the local machine if username can be found in the /etc/passwd file, or it is returned to the sender with a "User Unknown" error message.

When disconnected from the network, or when the alias map is only present in the files name service (as recommended earlier), you must specify mail recipient names to assure delivery. For convenience, you may enter aliases for the people or mail lists you frequently send mail to in the /etc/mail/aliases file.

amy: amy@travails
andrew: andrew@telco.com
bob: bob.roberts@therally
clark: clark@phonebooth
deskset: deskset@thehouse
jim: jim@cosmos
lyn: lynda@flanders
melissa: mfields@home
nomadics: nomadics@server.Corp
our-staff: myboss@hismachine
susan: susan@ct.amber.com
trish: trussell@bambus.COM

It is not necessary to remember, or otherwise determine, the fully specified name for people (or mail lists) who are not listed in the /etc/mail/aliases file. You can send mail to them by addressing it to user@mailhost where mailhost is the name of the mail host you defined earlier (for example, user@cosmos).

Do not use the actual word mailhost in the host part of the address since that can cause your mail to be misdirected.

You may address your mail to user@domain if your site uses DNS (e.g. jsmith@eng or jsmith@some.com).

Sometimes when an alias cannot be expanded, the mail is delivered to the local machine. This usually occurs because the cache in sendmail becomes unsynchronized with the actual configuration of the system. It may not happen very often or even at all, but occasionally it is a good idea to inspect the /var/mail directory for lost mail.