Plussed Detail Addressing

Plussed detail addressing is a simple way to achieve more versatile aliasing. It is available only with V8.7 sendmail and above, and it requires that you use a configuration file that comes with V8 sendmail. To illustrate its use, consider the need to have mail routed to different sets of administrators depending on how the address root is augmented:

root: hans, george
root+db:   root,
root+*:    root,

Here, the first line shows a normal sort of alias in which mail sent to root will instead be delivered to the local users hans and george. The second line is still not all that special because we could as easily have used an alias such as root_db to accomplish the same thing. It sends mail to root+db to the local root users and to the database administrators in another department,

The third line is where things start to get interesting. The +* in it will match anything or nothing following the plus, so mail sent to root+ will be sent both to the local root users and to the central administrators at But so will anything following the plus that is not db, such as root+foo.

If the +* form is omitted:

root: hans, george
root+db:   root,

the default for plussed addresses other than root+db becomes root. That is, when sendmail looks up a plussed address (for example, root+foo) it does so in the following order:

  • Look for an exact match. Does root+foo match root+db?

Get sendmail, 4th Edition now with O’Reilly online learning.

O’Reilly members experience live online training, plus books, videos, and digital content from 200+ publishers.