19

Say you own a abcd.com and you only want to use it to send and receive email via bob@abcd.com. You don't want to provide any kind of website.

Can you set up the DNS records to include an "MX" record and no "A" record?

  • Is this enough for sending and receiving email to work?

  • Is this valid in terms of whatever standard defines these things?


Edit: To clarify, the mail server (terminology?) would not be hosted on abcd.com or *.abcd.com

  • Amusingly, Google now does this routinely. GMail customers with a domain of their own, but without hosting, appear in DNS with a MX record but no A record. The MX record typically points to "aspmx.l.google.com". – John Nagle Jan 26 '18 at 1:38
33

As long as the system pointed at by the MX record has an A record itself, then yes.

For example: example.com can have a MX record pointing at mail.otherdomain.com. As long as the name mail.otherdomain.com itself is resolvable to an IP address, this is a valid configuration for example.com.

Strictly speaking, mail.otherdomain.com should be an A record with the IP address in order to be RFC-compliant. But this A record will be in the otherdomain.com domain, not in example.com.

Addressing your example, in order for bob@example.com to be a valid email address, mail.otherdomain.com needs to be configured to handle inbound mail for bob@example.com.

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  • 1
    mail.otherdomian.com MUST be resolvable by A record so this answer is incorrect – Jim B Jan 6 '10 at 15:39
  • 6
    The mail-only domain does not require an A record if the MX record points to an A record in another domain. The question is only about the mail-only domain. – Ben Doom Jan 6 '10 at 15:53
  • 1
    mail.otherdomain.com will have an A record in the otherdomain.com domain, not in the example.com domain. – David Mackintosh Jan 6 '10 at 16:53
  • nb - you can also just have an A record and no MX record and it will default to the A record. – Peter Scott Oct 31 '18 at 5:36
1

NO. The MX record points to a name. The names must be resolvable (via A record). The MX record should never point to a CNAME (RFC 1034 section 3.6.2, RFC 1912 section 2.4)

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  • 7
    True an MX records must point to an A record, but it doesn't have to point to one on the same domain. You could have the MX record for example.com pointing to mail.domain.com – Sam Cogan Jan 6 '10 at 15:08
  • that's not the question- mail.domain.com MUST have an A record. It's required both by RFC and by definition – Jim B Jan 6 '10 at 15:38
  • 1
    Jim -- The question does not specity that the mx record point to the parent domeain. For example, I could point bendoom.com's MX record to Google mail, and have no A records in bendoom.com – Ben Doom Jan 6 '10 at 15:52
  • Yes, mail.domain.com must have an A record, however he asked whether he needed an A record in abcd.com, if the MX record for abcd.com is pointing to mail.domain.com (or google.com etc) then he does not need an A record in the abcd.com DNS Zone – Sam Cogan Jan 6 '10 at 15:57
  • You are correct, that's what the clarification says NOW but not when I answered the question. There was no mention of another domain. It then goes on to what the standard says. In addition being resolvable does not mean it's a A record. That being said, most mail servers will still submit mail to a CNAME; however, you can't be guaranteed of it. – Jim B Jan 6 '10 at 16:45
1

It is possible - if mail over IPv6 ONLY is desired - as the AAAA record pointed at by the MX record satisfies the address target requirement. Granted, IPv4-only hosts won't be able to contact such a setup, but that doesn't make it illegal under DNS rules.

Why were all the prior answers so IPv4-centric?

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-2

Three ways to do this.

  1. Setup an MXE record. There should be a choice for an MXE record in the domain name server's mail setup section. This way you can point your MX to an actual IP address without creating an @ and www A record.
  2. Again, setup an MXE record. If the domain name server requires an @ and/or www A record anyway, point it to the domain name server's parking page.
  3. Again, setup an MXE record. Then point the @ and www A record to example.com, using the example.com IP address 93.184.216.34. When someone tries to go to your page, they will receive a '404 - Not Found'.

I do this on an IP/DN that uses a server's postfix virtual mail account. I didn't want my IP/DN to go to the virtual mail site's webpage. The above methods prevent that. Someone can pull the server's DN out of any received full mail headers and go there via that DN, however.

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  • MXE records are only valid with enom – Jacob Evans Nov 30 '16 at 15:34

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