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Sendmail, 3rd Edition by Bryan Costales

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Internal Mailing Lists

An internal mailing list is simply an entry in the aliases file that has more than one recipient listed on the right-hand side. Consider, for example, the following aliases file entries:

admin:  bob,jim,phil
bob:    \bob,/u/bob/admin/maillog

Here, the name admin is actually the name of a mailing list because it expands to more than one recipient. Similarly, the name bob is a mailing list because it expands to two recipients. Because bob is also included in the admin list, mail sent to that mailing list will be alias-expanded by sendmail to produce the following list of recipients:

jim, phil, \bob, /u/bob/admin/maillog

This causes the mail message to be delivered to the local users jim and phil in the normal way. That is, each undergoes additional alias processing, and the ~/.forward file of each is examined to see whether either should be forwarded. The recipient \bob, on the other hand, is delivered without any further aliasing because of the leading backslash. Finally, the message is appended to the file /u/bob/admin/maillog.

Internal mailing lists can become very complex as they strive to support the needs of large institutions. Examine the following simple, but revealing, example:

research:     user1, user2
applications: user3, user4
admin:        user5, user6
advertising:  user7, user8
engineering:  research, applications
frontoffice:  admin, advertising
everyone:     engineering, frontoffice

Only the first four aliases expand to real usernames. The last three form mailing lists ...

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