RRs for mail server

[Jukka Salmi]

I'm setting up resource records for a mail server. So far I have:

[...]
example.       IN  MX  mail.example.
foo.example.   IN  A   1.2.3.4
mail.example.  IN  A   1.2.3.4
[...]
4.3.2.1.in-addr.arpa  IN  PTR  foo.example.
[...]

The mail server uses mail.example as HELO hostname when sending mail.

I'm not sure if this is a valid setup, because if the remote mail server
does a reverse lookup for mail.example and then looks up the A record
for the address it got, he will get foo.example (and not mail.example
as used in HELO). If this is a problem I should probably change the MX
record to

example.       IN  MX  foo.example.


Any comments are appreciated!

TIA, Jukka

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