Viktor Dukhovni:
>
> > On May 5, 2017, at 8:48 AM, Georg Sotsas <georg.sot...@gmail.com> wrote:
> >
> > The mails sent to xxxx.x...@guilford.com remain in the queue with this
> > error:
> > Host or domain name not found. Name service error for name=guilford.com
> > type=MX: Host not found, try again
>
> This sounds like an error with *outbound* mail, please show the unredacted
> log entries (from the mail log, not "mailq" output), not just the error
> message. You can obfuscate email addresses, while otherwise leaving the
> error message intact.
>
> [ Wietse, this error was not related to the largish IP address count of
> the MX host, it was the actual MX RRset lookup that servfailed.
There is only one MX record for guilford.com, an that reply with
authority and additional records takes only 139 bytes.
I would not exclude the possibility that the OP is using a greedy
resolver that tries to look up A records when asked for MX, and
then reports an MX lookup problem when it was actually the A query
that failed because of the large response to that query.
Wietse
