Hi bighorton,
we also used canonical addresses for some time.
But actualy we changed our accounts to use personas.
This might be a good idea, because when upgrading your zcs to 6.0.7 you will not find a "canonical"-field in the adminUI any more.
(Have a look at
No more Canonical Address.. and now? )
How to do?
1. go to your adminUI
2. remove the canonical entry from one of your mailboxes
3. go to configuration::mail-options::mail-sending and mark "send mails from all addresses ok"
3. then go into this mailbox -> configuration::mail::accounts
4. enter your "canonical"-address into the special field for primary-account