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Presence of an MX record should _not_ be used as a litmus test for a valid email domain. RFC 5321 section 5 specifies that you lookup the MX and, if absent, us
by runlevel1 6y ago
Presence of an MX record should _not_ be used as a litmus test for a valid email domain.
RFC 5321 section 5 specifies that you lookup the MX and, if absent, use the A/AAAA record. I'm simplifying a bit, but that's the gist of it.
Using just the A record is more common than you might expect.
[1]: https://tools.ietf.org/html/rfc5321#section-5 https://tools.ietf.org/html/rfc5321#section-5