As was shown in the previous chapter, the
able to obtain its list of recipients from the
It can also obtain lists of recipients from external files.
In this chapter we will examine the two forms that those
external files take: the
A mailing list is the name of a single recipient that, when expanded by sendmail aliasing, becomes a list of many recipients. Mailing lists can be internal (in which all recipients are listed in the aliases file), external (in which all recipients are listed in external files), or a combination of the two. The list of recipients that forms a mailing list can include users, programs, and files.
admin: bob,jim,phil bob: \bob,/u/bob/admin/maillog
Here, the name
jim, phil, \bob, /u/bob/admin/maillog
This causes the mail message to be delivered to the local
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 above expand to real usernames. The last three form mailing lists out of combinations of those four, the last being a superset that includes all users.
When the number of mailing lists is small and they don't change often, they can be effectively managed as part of the aliases file. But as their number and size grow, you should consider moving individual lists to external files.