So the problem I mentioned in the previous post was not exclusive to LiquidWeb or Mail.app. All the issues seem to be related to an upgrade to CPanel which addressed a critical security vulnerability.

A few days after the LiquidWeb problems I ran into similar issues with sites hosted on SwiftCo.

Both hosting companies handled this poorly. Customers should have been notified that there would be an upgrade. Both tech support departments appeared to be caught off guard by the mail problems. While it is impossible to anticipate every potential interaction from a system upgrade, some advance warning would allow for these issues to be dealt with more effectively. Letting us know something was coming would also invite feedback which would help identify problems more quickly and help the companies better prepare responses and solutions whatever comes up.

I came very close to firing hosts and moving sites over this, not knowing the cause of our problems had me assuming incompetence.