Andrew Hodgson wrote:

However, over recent months we have had some issues with content filtering on some lists, with users who send emails with disclaimers, where the disclaimer is added as an attachment to the message, and Mailman appears to strip off the actual message, leaving the disclaimer to post to the list, and of course adding in the standard footer.

I suspect what is happening here is the poster sends an HTML only message. His organization adds a disclaimer as a separate MIME text/plain part and Mailman's content filtering is removing the HTML leaving only the disclaimer.

You can avoid this by adding text/html to pass_mime_types and making sure that collapse_alternatives is Yes so multipart/alternative with text/plain and text/html subparts is still replaced by only the text/plain and setting convert_html_to_plaintext according to your desire to have unfiltered HTML converted.

Are people using content filtering in lists where most people are using MS products, and a suitable antivirus package on the MTA as well as a low posting size limit, or are there any tweaks I can make to the content filtering settings that may get some of this stuff through?

Agressive content filtering can help with keeping viruses and other malware off the list, but a good malware scanner is probably preferable for that purpose. Content filtering is useful for keeping unwanted things off the list. Unwanted because you don't want to use bandwidth and archive space for images, HTML, proprietary document formats, whatever.

Note that if "most people" are using MS products, and they are not restricted, they will post .doc, .docx, .xls and .xlsx attachments. Where does that leave the minority who don't use MS products, not to mention those whose MS products are old enough that they can't handle the XML formats.

All MUAs can sensibly display plain text. The same cannot be said for other content types.

-- Mark Sapiro <mark@msapiro.net> The highway is for gamblers, San Francisco Bay Area, California better use your sense - B. Dylan