In a list I administer, the From line in an incoming email shows [Poster's Name] via [List Name] <address for posting a reply> . I use Outlook as my client, but at least some other clients behave similarly. However, I have at least one subscriber who uses Mozilla's Thunderbird as his client, and periodically the format changes to something else, most recently to just [List Name <address for posting a reply> . I suspect this occurs from some combination of the way Thunderbird parses the header and the way it populates some kind of address book that makes autofill work, but I'm not sure. Is this a known problem? Is there an easy fix that will be stable? In the past, putting an association in his address book and removing others worked, but it didn't hold and he is frustrated.