Notification of an error in delivery to a mailing list is sent to the original sender as bounced mail. Although this behavior is desirable for most mail delivery, it can have undesirable results for mailing lists. Because the list is maintained locally, it does not make sense for an error message to be sent to a remote sender. That sender is likely to be puzzled or upset and unable to fix the problem. A better solution is to force all error messages to be sent to a local user, regardless of who sent the original message.
When sendmail processes errors during delivery, it looks to see whether an "owner" was defined for the mailing list. If one was defined, errors are sent to that owner rather than to the sender. The owner is defined by prefixing the original mailing list alias with the phrase owner-, as shown in the following aliases file fragment:
nuts: :include:/home/lists/nuts.list owner-nuts: george
Here, nuts is the name of the mailing list. If an error occurs in attempting delivery to the list of recipients in the file /home/lists/book.list, sendmail looks for an alias called owner-nuts (the original name prefixed with owner-). If sendmail finds an owner (here, george), it sends error notification to that owner rather than to the original sender. Generally, it is best to have the owner- of a list be the same as the owner of the mailing-list file, because that user is best suited to correct errors as they appear.
To ensure that all errors in mailing lists are handled by someone, an owner of owners should also be defined. That alias usually looks like this:
If sendmail cannot deliver an error message to the owner- of a mailing list, it instead delivers it to the owner-owner.
Beginning with V8 sendmail, a single alias expansion is done on the owner- of any :include: list, and that expansion is made the address of the envelope sender:
nuts: :include:/home/lists/nuts.list owner-nuts: nuts-request nuts-request: george
Here, with V8 sendmail, the envelope sender for mail sent to nuts will be nuts-request (a single-level alias expansion), rather than george (a multiple-level alias expansion).
As a side effect, with V8 sendmail, mail sent to owner-anything will have the envelope-sender address set to a single alias expansion of owner-owner. This can be confusing, so always stress to users that they should mail the maintainer of a list with the -request suffix instead of the owner- prefix.