I started to run a self-hosted mail server which I want to be reachable via a subdomain only. I have an A record for mail.sub.domain.tld and an MX record for sub.domain.tld /edit: which points to mail.sub.domain.tld. (I also set up spf, dkim and dmarc TXT records for sub.domain.tld, dkim._domainkey.sub.domain.tld and _dmarc.sub.domain.tld respectively)
I have a couple of servers which I want to use with the domain. Could it be a problem for the acceptance of my email by other servers if the A record for sub.domain.tld points to a different ip as mail.sub.domain.tld?
What about if the same is true for domain.tld and foo.sub.domain.tld? I think at least the last one should be possible but I'm not super-confident in my understanding of DNS in general.
Best Answer
That should be fine. As long as the records relating to email match up in both directions, you can have other DNS records pointing to different IP addresses all you want.
For instance quite a common scenario would be to have inbound email delivered to
mail.sub.domain.tldon one IP address, and a website hosted on a different server/IP address pointing towww.sub.domain.tldandsub.domain.tld.Obviously if you're sending from the
mail.sub.domain.tldIP(s), and also have the website sending emails (for instance contact forms), then you'd need to ensure that both of them are included in your SPF record, so receiving servers see both as valid email sources.The same is true for
domain.tld, as you'd have separate MX / A / SPF records for that domain level, so they wouldn't impact each other. For instancemail.sub.domain.tldandmail.domain.tldcould have completely different setups and DNS records without negatively interacting with each other.If a receiving server got an email from
[email protected]it will specifically look insub.domain.tldfor an SPF record, not in the rootdomain.tlddomain that could be configured with completely different details.