While trying to troubleshoot why email wasn’t being delivered to one of my mail aliases on a new server this morning, I discovered a nifty little trick for testing the deliverability of an email address using exim from the command line.
exim -bt command line flag
From the command line enter “exim -bt” followed by the email address to test as shown in the example below, where I was testing the email address minerva@nz1.minervamail.com:
exim -bt minerva@nz1.minervamail.com
Mail to that domain was handled by the localhost and there was a system alias set up to send all mail to the “minerva” user to my email address. Unfortunately I had mis-typed my own email address in the /etc/aliases file so got the following result:
R: system_aliases for minerva@nz1.minervamail.com
R: dnslookup for chris@isavvy.co.nc
chris@isavvy.co.nc is undeliverable: Unrouteable address
<-- minerva@nz1.minervamail.com
Until I worked out how to do this, I had been confused about why mail was bouncing as the mail system appeared to be all set up correctly. It was only when doing this test that I saw it was actually the forwarding address causing the error.
After correcting the alias, running newaliases and trying again:
R: system_aliases for minerva@nz1.minervamail.com
R: dnslookup for chris@isavvy.co.nz
chris@isavvy.co.nz
<-- minerva@nz1.minervamail.com
router = dnslookup, transport = remote_smtp
host aspmx.l.google.com [74.125.95.27] MX=10
host alt1.aspmx.l.google.com [74.125.47.27] MX=20
host alt2.aspmx.l.google.com [74.125.115.27] MX=20
host aspmx3.googlemail.com [72.14.213.27] MX=30
host aspmx5.googlemail.com [74.125.157.27] MX=30
host aspmx4.googlemail.com [209.85.229.27] MX=30
host aspmx2.googlemail.com [74.125.43.27] MX=30
Some other examples
You can also use it for testing deliverability of remote addresses to, e.g.:
$ exim -bt test@example.com R: dnslookup for test@example.com test@example.com router = dnslookup, transport = remote_smtp host example.com [2001:500:88:200::10] host example.com [192.0.43.10]
and an invalid format address:
$ exim -bt test@@example.com syntax error: domain missing or malformed
and another example:
$ exim -bt test@test@example.com syntax error: malformed address: @example.com may not follow test@test
and finally an example where MX records aren’t set up for the host:
$ exim -bt foo@bar.com R: dnslookup for foo@bar.com foo@bar.com is undeliverable: all relevant MX records point to non-existent hosts