[Mimedefang] sending relay has no MX record?

Adam Lanier adam at krusty.madoff.com
Mon Jan 31 12:52:45 EST 2005

Hash: SHA1

David F. Skoll wrote:
| On Mon, 31 Jan 2005, Adam Lanier wrote:
|>Technically, a server can generate mail (legally according to RFC's)
|>without having an MX record.  Only servers that RECEIVE mail need to
|>have an MX record.
| They don't need to have an MX record; an A record will do.
| roaringpenguin.com, for example, has an A record.  If roaringpenguin.com
| had no MX records, then mail for foo at roaringpenguin.com would go to the
| A record.
|>What needs to be in place is a valid return path for the mail that is
|>generated.  So, while server 'mailout.example.com' can generate mail
|>from the domain 'example.com' with only an A record, some server
|>somewhere SHOULD (again, according to RFC's) have an MX record for the
|>domain 'example.com'.  If there is no MX record for the domain
|>'example.com' then the 'mailout.example.com' will be used as the return
|>path for the generated mail.
| No; if there's no MX record for "example.com", then the A record for
| "example.com" will be used, if it exists.  If no A record exists either,
| then it will be impossible to mail anyone at example.com
| --
| David.

Understood David and that's pretty much what my reply had said or, at
least, that's what I had intended it to say.

An MX record is required to RECEIVE mail not to send it.  An A record
will be used if no MX record is available.  Without an A record, no mail
can be sent to the domain in question.

The point being that checking for both an MX and A record is somewhat
pointless in regards to determining whether mail from the host is
'valid' or 'spam'.

- --
Adam Lanier
Bernard L. Madoff Investment Securities LLC
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