Cloudflare does not support RFC 7505 (null MX)

Hello,

E-mails servers seek for a MX records in order to identify the FQDN or IP address of a mail server. If there no MX records is found, the SMTP servers will consider the root A ADDRESS for that domain as the e-mail server and will attempt (and retry a couple of times) to connect to its mail ports to deliver e-mail as described in RFC5321.

This generates unwanted and unnecessary traffic for both endpoints. The standard way to avoid is described at RFC7505 in a very simple way: if a MX record with the value “.” (dot) is found, the SMTP will hard fail this delivery and will not attempt again for this domain because it clearly understands there is no e-mail server for this domain.

I’m trying to comply with RFC7505 for all my domains hosted at CloudFlare that does not have an e-mail sever but Cloudflare’s control panel gives me an error when I attempt to create a MX record with the dot value. The following error message appear:

“NS Validation Error (Code: 1004) Content for MX record must be a hostname.”

Could Cloudflare change its field validation algorithm to allow users to comply with RFC7505, please?

That’s weird. I do this in all my no-mail domains:

p.s. I just tested this by deleting and re-adding it. Still works.

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Interesting! If I use @ in the “Name” field (meaning the root domain) I get an error. But if I explicitly insert my domain at this filed, I am able to insert the “.” value at the “Mail server” field.

So this seems to me to be a just a frontend field validation issue at Cloudflare’s control panel.

I actually tested it with @ and it didn’t glitch.

What the ■■■■?! Now I’m not able to reproduce the problem. The @ works fine as well.

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