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Asked: 2010-01-07 06:55:44 +0800 CST

DNS: Is it valid to have an "MX" record and no "A" record?

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Say you own a abcd.com and you only want to use it to send and receive email via [email protected]. 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

domain-name-system email mx-record

4 Answers

  1. Best Answer

    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 [email protected] to be a valid email address, mail.otherdomain.com needs to be configured to handle inbound mail for [email protected].

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  2. 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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  3. 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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  4. 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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