How do I allow attachments to be sent to a Mailman list?
By default, a new "group discussion" Mailman list does not allow list messages with attachments. (An "announcement only" list does.)
One reason for this is that allowing attachments can theoretically allow harmful things like viruses to be posted (although our virus scanner will catch almost all of those). The other reason most mailing lists don't allow attachments is that many email programs send multiple versions of the message in different formats as multiple attachments, which may be annoying for some list members.
If you wish, you can allow attachments to be sent to your Mailman group discussion mailing list. To do so, just turn off "content filtering" in Mailman.
1. View Mailman's "Content Filtering" screen
Go to the management page for your list, then click Content filtering.
2. Disable filtering
Click No next to "Should Mailman filter the content of list traffic according to the settings below?"
3. Press the "Submit Your Changes" button
Your Mailman list will now allow attachments to be sent. (Note that this change also allows HTML messages and other non-plain-text messages.) The next step is to set a size limit for the attachment.
4. View the "General Options" screen
Click on General Options from the main screen.
5. Set an attachment size limit
Scroll down to the "Maximum length in kilobytes (KB) of a message body. Use 0 for no limit." and enter 10000 or a lower number, but don't enter 0 (Mailman has problems sending attachments larger than 10 MB). If you have a larger attachment then you should place it on your website and simply link to it in your message.
6. Press the "Submit Your Changes" button
Your list should now be correctly configured to allow attachments!