If you'd read your own thread, you'd know the answer already. Lyris is its own MTA - it speaks SMTP directly to the recipients' mail servers. This allows it to do on-the-fly customization at SMTP transmit time instead of having to queue each unique message.
Fair dues.
I'll make you a deal - you write the MTA, and I'll add support in mailman to offload the personalization.
I do not personally have the skills to do this but I wouldn't rule out trying to get the funding to help make it happen. I wonder if there is there enough collective know-how among Mailman developers and other interested parties.
Definitely. There are probably a six on this list who could write an MTA -- or have. The problem is, that dozen or so folks all (and I hope I speak for those people appropriately as I speak for myself) have come to the realization that it's rarely if ever cost-effective or worth the effort.
A secondary issue is there are more and more mutterings and grumblings that it's time to get serious and replace SMTP. If you integrate an SMTP server into Mailman and we go off and replace SMTP, where are you? out on a limb with a chain saw.
While Lyris has a lot going for it, it's tightly coupled MLM/MTA is a feature that's a mixed blessing. Now, if SMTP is replaced properly and the warts any MTA have to deal with (Hellow, Lotus Notes. Hello, exchange. hello, you know who you are) can get scraped off and not replaced with new warts, intefacing at the MTA level might be more practical.
But I wouldn't recommend it, support it, or encourage it with Mailman. not now, not in a year, not in five. Not to SMTP.
Mailman has a lot of things to do to become an even better mailing list manager before we should even think about trying to re-implement what the MTA teams are already spending all of their time on.
And I think we can do within Mailman what you think you need to integrate an MTA to do, without all of that pain and suffering. Or at least enough of it to not warrant going through the swamp to get there.
And trust me, SMTP is a swamp, with lots of hungry alligators.