Is there a way to stop them?

Since there are no standards for out-of-office (OOO) messages, how they are handled depends entirely on how the remote mail server decides to handle the OOO reply. LISTSERV can recognize some (but NOT all!) OOO messages and deal with them (i.e., ignore them). Other OOO messages get sent to the error-handling address for the list, and this can potentially cause LISTSERV to eventually auto-delete the user whose mail server is throwing back the autoresponse. Other OOO messages get sent back to the list address and can cause loops, which are easy enough to fix--you just delete the user or set him to NOMAIL. Still other OOO messages get sent back to the person who made the original posting (since his address is in the From: line), and LISTSERV never sees them at all. These last are the confusing ones because they sometimes make users think that their messages aren't being accepted by the list, when in fact their messages are being accepted but are being bounced by some other subscriber's OOO setup after LISTSERV sends them out.

Many list owners don't even mess with people who set OOO messages and go on vacation. They delete or NOMAIL the user as soon as they start seeing the messages or start getting complaints from other subscribers.  How to handle this, of course, is a decision that should be made locally.

LISTSERV does have a Content Filter template (look in the web interface under "Mail Templates", change "Template Categories" to "All Templates" and click the "Select" button, then find "CONTENT_FILTER" in the list of available templates.  For instructions on how to write rules for the CONTENT_FILTER template, see Content Filtering in the List Owner's Manual.

A CONTENT_FILTER for different sorts of OOO messages (and also one which rejects messages with blank subject lines) might look like this:


Action: REJECT Please resubmit your message with a non-blank subject.

Subject: out of office

Action: DISCARD Probable OOO message

Subject: out of the office

Action: DISCARD Probable OOO message

Subject: Auto-Generated:

Action: DISCARD Probable OOO message

Subject: AutoReply:

Action: DISCARD Probable OOO message

Precedence: junk

Action: DISCARD Probably OOO or other non-germane message

However:  It is highly important to be judicious about adding conditions, not only for OOO messages, but for any filter you might want to add.  It's entirely possible that a perfectly legitimate message might contain a phrase that matches a filter you have inserted, and could be dropped or rejected when it should have been allowed.  For instance, someone might write an email to a list in which they simply want to let people know they will be out of the office from some date through another date, and might phrase that as "Hi, everyone, I will be out of the office starting Friday and won't be back till next Wednesday."  This filter that scans the body of the message for a particular phrase:

Text: I will be out of the office

Action: DISCARD Probable OOO message

would cause that message to be discarded, without any notification to the person who posted it.  If that person is your CEO, they might be a little miffed that their message didn't go through.

Another example of why one must carefully think filter conditions through would be an attempt to block spam messages with the well-known drug Cialis in the subject line:

Subject: Cialis

Action: DISCARD Cialis spam

This would seem like a noble effort to cut down on spam, but unfortunately, it would also match the word "speCIALISt".  As in, "Subject: Need a specialist to help me fix this problem."

So, please be careful when writing filters and conditions.