[Solved] Troubleshooting mail server issues

Discussion in 'Server Operation' started by anark10n, Jul 7, 2017.

  1. anark10n

    anark10n New Member

    Hey, there
    So, I'm experiencing some mail server issues that I'd like to figure out the cause of.
    Firstly, delivery to certain domains (gmail, hotmail), in that when I send a message, I will receive a confirmation that it was sent, but I don't receive it at the destination, with no bounce back message to my server.
    Secondly, for some of the domains it is able to reach, the message will go the spam folder, even though my mail server is not blacklisted, and the message will still go to the spam folder even after I mark the message as not spam and to allow messages from the domain.
    How would I go about looking to resolve these issues.
     
  2. Stephan Ververda

    Stephan Ververda New Member

    First: For the non delivery, how do you recieve confirmation it was sent? how do you send the mail (client). The fact their is no bounce back message can be because for example mail delivery has been delayed (in that case it can take few days before you actually get a bounce message or anything). Did you check the mail.log, mail.err, mail.info, mail.warn files?
    Does the mail that has been sent contain a reply-to address or not, is the send from address a correct one (basically in a client you could define a different FROM address than the actuall user, and there can be an error in that address), this can be of influence of recieving or not a bounce back mail.

    The second problem can become very complex, but basically it has everything to do with the reputation of your domain and the reputation of the outgoing SMTP server (the ip address). For starters you have to check the e-mail headers of the recieved mail (how to do that depends on the recieving client) to see if there is a spamscore in the header. The determination of the spamscore comes from multiple sources, like i said the reputation of the domain (a new domain for example cannot have a good reputation yet, but neither a bad one), the reputation of the ip of the sending SMTP server, how does the PTR record of that IP resolve (is it the same name as the name of the SMTP server?), are there multiple domains on that IP? (they will all influence the reputation). Is there a DKIM record in your DNS, is there an SPF record in your DNS (is that ip allowed to send on behalf of that domain?).
    Furthermore it will obviously check the contents of the message, the subject (for instance the absence of a subject can already negatively influence the spam score). So per definition the mail server does not have to be blacklisted but still can have a negative reputation. That could even have been caused because the same IP has been previously used by another mail server that caused a lot of spam.
     
  3. anark10n

    anark10n New Member

    Ok, thanks for the advice about the mail logs.
    The thing about the delivery though is that I used to be able to send all these other mail domains, gmail, hotmail, etc., but now I can't. I can wait for days and the mail will never arrive. I remember this happening for another unknown domain and then suddenly, the other side could receive my messages after they first sent me a message.
    Regarding the reputation of my domain, I have an SPF, DKIM, and PTR record set correctly, as testing them with various services return a favourable response, namely mail-tester.com. Going to check a few others just to be sure. Thanks again for the advice.
     
  4. anark10n

    anark10n New Member

    Ok, just checked my server reputation again, and it appears my messages aren't getting the DKIM headers signed. I followed this tutorial on how to configure DKIM but both mail-tester and verifier.port25.com report my messages aren't being signed. My server runs on Debian 8 same as in the tutorial.
     
  5. sjau

    sjau Local Meanie Moderator

    Isn't DKIM meanwhile included in ISPConfig?
     
  6. anark10n

    anark10n New Member

    yes, but i didn't configure dkim through ispconfig. would this be a problem?
     
  7. sjau

    sjau Local Meanie Moderator

    No idea...
     
  8. anark10n

    anark10n New Member

    Figured out my problem. It was a problem with the syntax in my KeyTable file
    Code:
    default._domainkey.openitmation.com openitmation.com:default:/home/adminmator/opendkim/keys/openitmation.com/default.private
    Should have been:
    Code:
    openitmation.com openitmation.com:default:/home/adminmator/opendkim/keys/openitmation.com/default.private
     
    Stephan Ververda likes this.
  9. Stephan Ververda

    Stephan Ververda New Member

    Did you solve both problems with this?
     

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