Installing and Administering Internet Services
Chapter 4 131
Installing and Administering sendmail
Creating sendmail Aliases
Configuring Owners for Mailing Lists
Because the sender of a message often does not control the mailing list to
which the message is addressed, sendmail allows you to configure an
owner for a mailing list. If sendmail encounters an error while
attempting to deliver a message to the members of a mailing list, it looks
for an alias of the form owner-mailing_list and sends the error message
to the owner. For example, if mike were responsible for maintaining the
chess_club mailing list, he could be configured as the owner:
chess_club: mike@chem.tech.edu, marie@buffalo,
bigvax!amlabs!denise, margaret@hp.com
owner-chess_club: mike@chem.tech.edu
Any errors sendmail encountered while trying to deliver mail to the
members of the chess_club mailing list would be reported to mike.
Avoiding Alias Loops
You should avoid creating aliasing loops. Loops can occur either locally or
remotely. Following is an example of a local alias loop:
#Example of a local aliasing loop
first : second
second : first
When regenerating the alias database, newaliases does not notice a
loop like the one shown in the previous example. However, after the alias
database is generated, mail addressed to either first or second is not
sent. If the only recipients for the message are in local alias loops, the
message is returned with the error message All recipients
suppressed.
In the previous example, if mail is addressed to first, first expands
to second, which expands to first. This causes sendmail to remove
first from the recipient list as a duplicate.
# Example alias entry on host sage
dave : dave@basil
# Example alias entry on host basil
dave : dave@sage
Following is an example of a remote aliasing loop:
Mail sent to dave at either host sage or host basil bounces between
the two systems. sendmail adds a tracing header line (Received:) with
each hop. When 30 tracing header lines have been added, sendmail
recognizes the aliasing loop and aborts the delivery with an error
message.