I discovered this problem when renaming a user account in Zimbra 6.07
User email@example.com got married and needed to be renamed firstname.lastname@example.org
The rename is easily done in the ZAC, however when the user sends or replies to an email it is still being sent from email@example.com
Fiddling around with personas in Outlook or webmail did not fix this problem.
Personas worked when i set it to firstname.lastname@example.org or email@example.com but not jane.black@mydomain even when i created a persona with jane.black as a persona.
The only way i could fix this was to use the zmprov command.
zmprov ga firstname.lastname@example.org | grep -i canonical
zmprov ma email@example.com zimbraMailCanonicalAddress firstname.lastname@example.org
In summary 6.07 removed the canonical address from the ZAC however renaming user accounts from the ZAC does not rename the canonical address.
Headaches for me but hopefully useful to know for others.