Yup, this sounds like mail-in content to me, which is what I'm after :-)
If the goal is mail-in content, I'm not sure I understand IMAP to be anything approaching what you want: IMAP doesn't ACCEPT messages, at least not any of the IMAP servers I've seen, it serves messages up to clients (one of which could be Zope, like WorldPilot does). MailMan supports external archivers (how, I don't know, just saw it mentioned), and with the right archiver plugged in, that would give you the capability to archive email lists however you wanted. Also, I saw mention of someone using a script to archive msgs via WebDAV from mailman. The same sort of script could be used with any inbound MTA (postfix, qmail, sendmail, exim, etc...). Here's a URL to the post in Mailman-Developers: http://www.python.org/pipermail/mailman-developers/2000-February/001826.html
I have written an archiver that uses WebDAV to archive messages [with or without decoded attachments] to a WebDAV enabled web server. I'm currently using Apache, but there is no reason why it shouldn't work "out of the box" with Zope (Zope has a WebDAV enabler).
Email if you want patches/code... it works *very* well. We will be going into full production with it in the next week [www.bebusy.com].
A webdav-aware script, without mailman, could give you very simple mail-in access to Zope. With Mailman, a full alternative archiver. I'm just getting started with Zope, so I won't be coding this up, but hopefully this is enough for someone else to go on. Also: I'd like to voice some opposition to expending the effort to turn Zope into a full-blown SMTP MTA -- that's a lot of effort to down the "not-invented-here" path, complete with its' own security issues, etc, to be tackled. Building on other mail systems with proven scaleability (i.e. what happens when your Zope store is getting 100,000 message an hour?) makes more sense to me. Seems to me that tools to integrate Zope with existing mail tools would see the widest use. Thanks, Karl