Domain IP different from Exim IP

Answered

Jman

• January 11, 2025 15:41

Hi, all,

I need to temporarily migrate a domain's website away from its cPanel installation to an external IP, but will continue serving email.

Currently RDNS for the domain points to the same IP as the mail server, but once this happens, they'd be different.

In this situation, what are the best practices to ensure that outbound domain email doesn't get flagged as spam?

• 

  Jman

  • January 11, 2025 15:44

  Oh, I'd thought up just making an A record for www. and using htaccess on the cPanel site to redirect if someone just hits the bare domain, but somehow that doesn't sound like the best practice.

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• 

  quietFinn

  • January 11, 2025 16:21

  Usually emails sent from the server use the server's public IP, and if that's the case you don't need to worry about the rDNS.

  Also usually the MX record for the domain points to the domain, i.e.;
  yourdomain.tld MX 0 yourdomain.tld
  so that will not work.
  You must set:
  mail.yourdomain.tld A <server IP>
  and
  yourdomain.tld MX 0 mail.yourdomain.tld

  This assuming that DNS of yourdomain.tld is hosted in the server.

   

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• 

  Jman

  • January 12, 2025 20:51

  Hi, quietFinn, thanks for your reply.

  Usually emails sent from the server use the server's public IP

  That's where I'm getting hung up.  As I understand it, the "public" IP is wherever the website lives.  Perhaps that's my error in thinking.

  Currently domain.tld, www.domain.tld, and mail.domain.tld are all the same IP.

  By changing domain.tld and www.domain.tld to this external IP, they'd no longer match.

  You must set:
  mail.yourdomain.tld A <server IP>
  and
  yourdomain.tld MX 0 mail.yourdomain.tld

  The DNS zone is already configured that way.  An "A" record exists with the current cPanel IP for mail.domain.tld, and an MX record for domain.tld points to mail.domain.tld

  That being the case, once I update domain.tld and www.domain.tld's A records to the new IP, will email deliver-ability be affected?

  Sorry to be so obtuse; all this makes sense and matches what I'd read elsewhere.  Just don't want to mess up email once the website itself is on a different IP.

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  quietFinn

  • January 12, 2025 21:03

  >That's where I'm getting hung up.  As I understand it, the "public" IP is wherever the
  > website lives.  Perhaps that's my error in thinking.

  No, the "public IP" is what you see in WHM -> Server Configuration -> Basic Webhost Manager Setup -> Basic Config.
  If the websites domain resolves to different IP it does not change that "public IP".

  >The DNS zone is already configured that way.  An "A" record exists with the current
  >cPanel IP for mail.domain.tld, and an MX record for domain.tld points to mail.domain.tld

  >That being the case, once I update domain.tld and www.domain.tld's A records to
  >the new IP, will email deliver-ability be affected?

  No. What you described is correct and commonly used configuration.

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  Jman

  • January 12, 2025 21:23

  Ah, thanks for the clarification.  The public IP is actually different as I have four bound to this cPanel installation and this particular domain is on its own account, with mx, etc. records  all matching to that account's IP.

  Actually, the SPF records have both the main public one and the account's IP's, even though Exim is set to send mail from the account’s IP.

  Take care!

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