On 11/22/05 12:18 AM, "Stephen J. Turnbull" <stephen@xemacs.org> wrote:
Speaking for myself, I see nothing wrong with asking the bleeding edge adopters to change MTAs, and I see nothing wrong with restricting Mailman-supplied MTA code to a couple of MTAs that we "like". Of course we help other MTAs to incorporate the feature, but we don't need to promise that they can use it in advance. Some MTAs may never get it.
None of what I'm about to say is meant to imply that the idea being discussed is bad. Because I don't think it is a bad idea.
You're ideas are workable, but not--easily--here. Mail from the world and from customers arrives (into different Exim instances) on machine 1 (which is multiple machines in practice); the mail for mailing list addresses is then sent to the machine running mailman (machine 2). Machine 1 does not run a web server, and is unlikely ever to do so (mail storage and retrieval being over on machine 3, where web servers run for webmail only).
We don't (now, but could) do a recipient-verification callout from machine 1 to machine 2 for mail coming from the world (*), but only the addressing would be available, not whatever content-based rejection is desired in the Mailman configuration. (We also could let the world talk directly to the Mailman machine, at the cost of duplicating our greylisting (which keeps most spam and many viruses out of Mailman) and virus filtering and supplementary spam filtering on that machine. We'd have to see a major benefit to do that.
- Also, unless one's collection of local users uses non-majority MUAs (any MUA other than Outlook and Outlook Express is statistically insignificant in the general market), it's not a good idea to reject at SMTP time for submissions from one's own users, because the MUAs do such a rotten job of informing the user about the error. (Further, some send pending messages before retrieving, so the ISP gets support calls about "I can't get my mail" when the problem is that they are trying to send a message with a bogus address and don't realize that the odd little thing down in the corner is trying to tell them that.
So, at the MTA end, it's likely that for all-purpose ISPs, only some incoming email bound for Mailman will be checked at SMTP time (so Mailman will continue to have to check as it does now). Non-connectivity Mailman host operations--unless they accept message submission directly from MUAs--won't have that problem.