LISTSERV contains a configurable MIME attachment filter that will let you bounce or strip MIME attachments. The filter is configured on a list-by-list basis by using the new Attachments= list header keyword. (There is no site-wide override.) See the Site Configuration Keyword Reference for information on how to configure Attachments=.


Note carefully that Attachments= works only for properly-configured MIME attachments.


Also note that the Attachments= setting will not block old-fashioned uuencoded files that are not attached via MIME.  Because very few mail clients use uuencoded attachments anymore, LISTSERV simply strips uuencoded files from all messages by default.  You can re-enable this if necessary by setting Attachments= All rather than Attachments= Yes (see the documentation for details).


Note that you can also strip HTML attachments from multipart/alternative messages (assuming that there is a plain text alternative in the message) by setting Language= NoHTML in the list header. The Attachments= keyword setting cannot be used for this purpose, nor can it be used to strip or reject messages of MIME type text/plain (which are always accepted since they are plain text).


Finally, LISTSERV also strips by default proprietary Microsoft Exchange attachments which contain information about the mailpiece that is only usable by Microsoft Outlook.  The choice to strip these attachments by default was for the convenience of users who do not use Outlook and find the "winmail.dat" and MS-TNEF attachments produced by Exchange to be a nuisance.  However, in some cases it may be desirable to allow the Microsoft attachments through (for instance if all of your users are using Outlook and want the full experience), and this can be done by setting


Misc-Options= KEEP_EXCHANGE_DATA


in the list header.


A list of registered MIME media types for attachments is kept by IANA and can be found at


http://www.iana.org/assignments/media-types/index.html