Brad Knowles wrote:
This user is probably sending out an HTML-formatted message (or in some other MIME format), and you have Mailman configured to strip HTML (or whatever the other MIME format is).
Check your settings. Have the user send you a message directly, then use whatever techniques your MUA allows you to have to see all the messy headers and MIME body structure. If you don't have an MUA that lets you see all that, you'll need to get an MUA that will.
Brad is correct, particularly about diagnosis. I just want to add a couple of ideas.
If Mailman's content filtering removes ALL the MIME parts so none remain, the post will be handled according to filter_action; it won't go to the list. If content filtering is removing the body, there must be some other part which may be blank but is not removed for the result to go to the list.
Another possibility to consider is that the message may be an HTML or other rich text format message which is reaching the list and which has (for example) white text on a white background. If this is the case, the "blank" message body may be sizable to the point that it has a scroll bar, but still "blank". You may be able to select the "blank" text, copy it and paste it into a plain text editor and see it that way.
This latter situation comes about when someone has their own MUA set for "rich text" with a default background color of say black and an explicit font color of white. Then, when the white on black message is viewed by someone whose MUA backgrownd color is white, she sees the white on white "blank" message.