I've set up a fresh instance of postfix to act as the backup MX to my domains, using a mysql back end.

I've loaded the db table that the relay_recipient_maps setting in postfix looks at with my users and my defined aliases/forwardings (i.e., sales@ goes to bob@) and if I block SMTP from all but the backup MX in my firewall, mail still arrives (with a slight delay).

But I'm also using the recipient_delimiter feature/option to provide users the ability to generate their own unique address (i.e., me-stackexchange@example.com the mail gets to me@example.com) on my primary MX.

Since there could be any of those, created by users on the fly, how can the backup MX receive and process mail intended for those addresses?

  • If you think postfix is bad, I think you are right. However, the problem is that it is the least bad I know. All the alternatives are still far worse. I simply can't understand why a simple ruleset for incoming/outgoing/etc mails, maybe in a chained data network structure, wouldn't be enough. But it isn't. On postfix, at least the traces are visible that somebody, sometimes, tried it originally.
    – peterh
    Aug 19, 2017 at 23:23
  • Nothing wrong with postfix - afaik it does a great job of handling my mail for multiple users and multiple domains, does decent spam scanning by passing off to spamassassin, viruses via amavis, and passes mail off to dovecot or courier to be delivered to teh end user. Just trying to figure out how I can deal with the user-created-on-the-fly aliases.
    – ivanivan
    Aug 20, 2017 at 0:06
  • 1
    Please explain your problem better. Why can't you just add the recipient delimiter setting to your backup MX?
    – sebix
    Aug 20, 2017 at 8:15
  • @sebix - for some reason I'm thinking that the recipient delimiter was for mail accounts actually hosted on that box, not for backup mx purposes. Will run off to test.
    – ivanivan
    Aug 20, 2017 at 12:36


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