Sendmail, 3rd Edition

Problems with Mailing Lists

At small sites that just use mailing lists internally, the problems are few and can be easily solved locally. But as lists get to be large (more than a few hundred recipients), many (more than 50 lists), or complex (using exploders), problems become harder to localize and more difficult to solve. In the following discussion we present the most common problems. It is by no means comprehensive, but it should provide information to solve most problems.

Reply Versus Bounce

The eventual recipient of a mailing-list message should be able to reply to the message and have that reply go to either the original sender or the list as a whole. Which happens is an administrative decision. In general, replies go to the address listed in the From: or Reply-To: headers. If the intention is to have replies go to the list as a whole, these headers need to be rewritten by a filter at the originating site:

list:   "|/etc/local/mailfilter list -oi -odq -flist-request list-real"

Here, the name of the filter has replaced sendmail in the aliases file entry. Writing such a filter is complex. The original addresses need to be preserved with appropriate headers before they are rewritten by the filter.

The converse problem is that not all mail-handling programs handle replies properly. Some programs, such as UUCP and certain versions of emacs-mail, insist on replying to the envelope sender as conveyed in the five-character "From " header. By setting up lists correctly (as we showed earlier), ...