> *The domain has a null MX record (indicating it doesn't accept email)* Not qui... | Hacker News

Hacker Newsnew | past | comments | ask | show | jobs | submit

		emmelaich 3 months ago \| parent \| context \| favorite \| on: Microsoft mishandling example.com > The domain has a null MX record (indicating it doesn't accept email) Not quite true, SMTP will use the A record if there is no MX.

dpifke 3 months ago [–]

In this case, "null MX record" means MX exists, but does not specify a valid server:

   $ host -t mx example.com
   example.com mail is handled by 0 .

Senders should not fall back on the A record in this case.

Consider applying for YC's Summer 2026 batch! Applications are open till May 4
Guidelines | FAQ | Lists | API | Security | Legal | Apply to YC | Contact