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Thread: Why does Postfix need to use an SMTP relay?

  1. #11
    Join Date
    Apr 2020
    where the work takes me
    Ubuntu 20.04 Focal Fossa

    Re: Why does Postfix need to use an SMTP relay?

    Quote Originally Posted by SeijiSensei View Post
    Postfix doesn't need a mail relay, but if it doesn't send its mail through a well-regulated relay, the mail is likely to be refused.

    To avoid using a relay you would need, at a minimum, both forward and reverse DNS resolution set up for the machine running Postfix. You will also need a domain name with an associated SPF record that indicates the machine running Postfix is a valid sending server for the domain you choose. These days using DKIM to sign your mail is becoming de riguer as well, especially if you have recipients in some of the big domains like or Easier to send your mail through a valid relay server.

    If you intend to send the mail directly from your machine, please visit to run its variety of security tests.
    Thanks, I don't think I need all of the provisions you mention, just because I'm only using it to forward mail onto my webmail providers SMTP server, it will basically work in one direction and never actually receive any replies (I don't even have a domain name). As I said in my reply to @TheFu above, my initial tests have been a success!

    I will visit mxtoolbox and see what tests they offer though, I did read the Postfix SASL documentation carefully and configure it to basically be a selfish server that only serves local email clients (as in very local, as in just my little desktop). My main concern was that I would get the home IP address on some sort of spam blocker list I think I've covered all of the important bases though.

  2. #12
    Join Date
    Mar 2010

    Re: Why does Postfix need to use an SMTP relay?

    Quote Originally Posted by jcdenton1995 View Post
    I think I will be okay, as, like you mentioned, my webmail's SMTP server listens on port 587 and I do authenticate with it, so my ISP may just let that sail through!
    587 is for client -to- server SMTP transmissions. No ISP should be blocking that. Thunderbird and MS-Outlook and probably every other thick email client support that port for sending authenticated email. DHCP doesn't matter. It only matters when we are trying to send server-to-server emails without credentials.

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