Hello, I've been running a small volume Postfix mail server on a fixed IP for 15+ years or so.
Recently, my provider forced me from ADSL (being phased out here) to VDSL, and I now find myself sending mail from a "dynamic" IP address... As expected, some destinations refuse to accept my outgoing mail with a 550 (usually with a "you're blacklisted" message on top of it). So, I am now looking for some magic that would make Postfix: a) first attempt to deliver outgoing mail straight to the destination MX (as it does now), and, b) if that fails with a "550 Bad IP" (or equivalent), fall back to my ISP relay server and send it through them. These 2 steps would have to happen for each message separately, every time. Even if the destination doesn't like my IP right now, it might accept it in a few hours from now (happened this morning). Ideally, that mechanism should be able to "predict" if it's worth a relay attempt. For example, relaying will (hopefully) fix a "550 This IP is blacklisted", but it won't help with a "550 No such user". The "smtp_fallback_relay" param does not seem suitable for this, as the destination host *can* be found and *is* reachable, it's just being rude to me <g>. I am currently "fixing" it with a transport map for the "rude" domains (such as postfix.org <g>), but that is only a stopgap measure. If my IP changes next week, other domains may dislike the new one although they had no problems with the one before it. Relaying *all* the outgoing mail through my ISP is *not* an option. As long as the message sits on my own box, I can see what's going on (e.g. greylisting). And if it's handed from here to the destination directly, I have all the details on hand to help them debug it at their end. But I loose all that control when I hand the message over to my ISP. So please, no philosophical arguments, I promise I won't be impressed <g>. To paraphrase: relaying through my ISP *must* be kept to an absolute minimum, along the lines described above. The question is: does Postfix have something like this ? Or do I have to write something myself? If yes, any suggestions? I have been RTFM, peeking in the smtpd.c client source, pondered about a special bounce handler (to detect "bad IP" and forward to my ISP), thought of playing with "smtp_dns_reply_filter" (add the relay server at the end of the "real" MX's) etc., but had no "AHA!" experiences yet. I will continue my search, but I thought I'd ask here as well, just in case this wheel has been invented already. If not, building a new one would certainly be cheaper (for me) than obtaining a fixed IP. If available at all, they cost an arm and a leg over here. Better keep my 2 arms and use them to type some code NB: I'm running Postfix 3.2.0 now. Upgrading to 3.3.1 is planned, but (from the readme) currently as low priority. Many thanks in advance, Luc
