I just found the "Check MX Record" button on the domain in the admin console and clicked it to see what it did. Much to my surprise it told me that it had failed. I know that the DNS records are correct so I clicked on the details to see what it was finding and saw this:
Anybody have a clue as to how those are different at all?
Domain is configured to use SMTP host: email.pyxislab.com. None of the MX records match this name.
Found the following MX records:
(I also tried with "zimbraPublicServiceHostname: email.pyxislab.com.")
zimbra@email:~$ zmprov gd pyxislab.com | grep -i publicservicehostname
zimbra@email:~$ dig +short MX pyxislab.com
From what I can tell this button just doesn't work...which isn't much help to people who might actually have issues.