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Tl dr; Is it possible to receive email for aliases of multiple domains on a single KVM?

I had a Digital Ocean server with multiple websites hosted on it, and needed email aliases of more than one of those domains. On several occasions, mail was not delivered, I believe it's possible that this is because the corresponding domain did not use a PTR record (Could be wrong.)

The PTR records with DO are tied to droplet names, so it seemed impossible to have PTR records for multiple domains, thus I was stuck with incomplete MX records and that may have been the cause of my undelivered mail.

I was thinking, there must be a way around this issue, besides renting another KVM.

Dave M
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Glenn
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1 Answers1

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Yes.

I'm not sure what you mean by "aliases', as this is usually referring to an email address the server can accept mail for, but will deliver the mail to a different user.

The PTR record in the context of a mail server is only for the purpose of Fordward Confirmed reverse DNS (FCrDNS) checks, which is performed only as a "proof of work" on a sending server by a receiving server. When used, it is only the address of the sending server domain (typically the hostname of the server such as mail.example.com). The PTR record will have nothing to do with your MX records and FCrDNS for your server will have nothing to do with receiving mail on your server.

The solution is to review /var/log/mail.log and determine what happened when the mail was delivered to the mail server and then fix that problem.

Paul
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  • Thanks for your reply.

    By "aliases of myltiple domains", I mean: user1@domain.tld, user1@domain2.tld, user1@domain3.tld, etc. I really need ptr records for all of these, don't I? Is this possible on one KVM? If so, how can I implement it?

     – Glenn Apr 20 '21 at 09:01
  • I reviewed the log at the time and there was no mention of a mail being dropped, at all. I tried to investigate and got a relay access denied error.

    The other reason I may have missed emails was a) if the sender's email wasn't verified or b) Because I hadn't setup a mail server in a seperate .mail subdomain, which I understand to be the best practise.

    I have opened a new, related question: https://serverfault.com/questions/1060920/how-do-i-set-up-a-mail-server-in-a-mail-subdomain

    Thanks for helping me get to the bottom of this! :)

     – Glenn Apr 20 '21 at 09:01
  • "When used, it is only the address of the sending server domain (typically the hostname of the server such as mail.example.com)." - so if mail.domain.com is my main mail server address, and i send an email from glenn@gnn.com i.e. a different fqdn, will it impact my chances of the email landing in spam (I think, yes)? How can I mitigate this without purchasing an additional KVM? – Glenn Apr 20 '21 at 09:16
  • The sending server domain is always how the server will identify itself to receiving servers. For your purposes, there is only one sending server domain for all email sent from the server. The sending server can be authorized by other domains to send mail, but the server will not identify itself as those other domains. – Paul Apr 20 '21 at 15:46
  • Yes, I understand that. So are there any measures I can take to help prevent my emails landing in recipient spam folders? – Glenn Apr 20 '21 at 16:21
  • All you can do is configure to reduce arriving in spam folders, but there is no way to prevent it. You can search here on SF and elsewhere to discover the various best practices. – Paul Apr 21 '21 at 14:01