Zimbra does not notify us when MX lookup failed.

[sunny.4d]

Had a problem today where our DNS server did not resolve the MX record of the domain of an email address we are trying to send to. The DNS server has been fix now, but the problem with Zimbra is that we are not aware of this problem until one of our client said that they did not get an email from us.

Now if I do send an email to invalid@invalid.invalid, zimbra does tell us about this in an email:

I'm sorry to have to inform you that your message could not
be delivered to one or more recipients. It's attached below.

For further assistance, please send mail to postmaster.

If you do so, please include this problem report. You can
delete your own text from the attached returned message.

                   The mail system

<invalid@invalid.invalid>: Host or domain name not found. Name service error
    for name=invalid.invalid type=A: Host not found

Is it possible to configure Zimbra to send us a message if it for any reason were not able to send an email?

Relevant logs: (client address replaced by example@example.org)

May 30 15:53:29 zimbra postfix/smtp[5974]: 0FA8F9E0333:
to=<example@example.org>, relay=none, delay=0.04,
delays=0.01/0.01/0.02/0, dsn=4.4.3, status=deferred (Host or domain name not
found. Name service error for name=example.org type=MX: Host not found,
try again)

May 30 16:01:19 zimbra postfix/smtp[8009]: 0FA8F9E0333:
to=<example@example.org>, relay=none, delay=470, delays=470/0.01/0/0,
dsn=4.4.3, status=deferred (Host or domain name not found. Name service
error for name=example.org type=MX: Host not found, try again)

May 31 15:14:40 zimbra postfix/smtp[13238]: F3E429E04CF:
to=<invalid@invalid.invalid>, relay=none, delay=0.25, de
lays=0/0/0.24/0, dsn=5.4.4, status=bounced (Host or domain name not found.
Name service error for name=invalid.in
valid type=A: Host not found)

[ewilen]

You may want to lower your delay warning time as described here.