Since the problem is a relative handful of large attachments, could a solution just be to provide a repository for mailing list members to store such files, yielding a URL they could use in an email ? Then, the usual list feedback would keep the attachment sizes manageable.
(*mumble*) Folks, let's please not try to engineer around user silliness. User silliness will occur no matter what tools we provide.
Anybody can get a place on Dropbox or elsewhere and put a URL to their stuff into an email message. The problem is not that the tool isn't there. The problem is that people don't use it. They attach dumb things instead of pointing to them. Or worse they paste them inline, making it even harder for people who use tools that can avoid attachments from having to deal with them. What we need is better decisions and a bit more considerateness by senders of email, not more things to let them continue being dumb.
And there is no "one size fits all" solution here: Setting up a separate list that strips out attachments and makes them links helps me some of the time (when I'm on a low bandwidth device that can't receive mail other than in lump-and-dump mode), but it's lousy for me at other times (when my device is now zero bandwith and I would have liked everything downloaded while I was online so now I can read it offline). Maybe some folks are never offline (or are willing to ignore some of the data that was sent while they are), or simply don't have access to tools that allow them to only download attachments on demand. Maybe a second list with this feature would help. But overall, this seems like a social engineering problem more than a computer engineering problem to me.
All of this is independent of an IMAP archive. That let's people manipulate message in the archive with their favorite email program, downloading attachments (or not), replying (and getting all of the References: header fields right), etc. That's a good thing for the recipient, independent of this issue.
pr -- Pete Resnick<http://www.qualcomm.com/~presnick/> Qualcomm Incorporated - Direct phone: (858)651-4478, Fax: (858)651-1102