The canonical address displays in the 'From:" field of messages that are sent.
So say your user account is:
last@domain.com
You could have a
canonical to make it permanently look like mail is coming from:
first.last@domain.com
To take the place of a fixed canonical address you can also user mail identities (in the option tab of each user) so the user can select when they want to appear as
first.last@domain.com or
first.m.last@domain.com or just
last@domain.com Mail Identities are for appearing to be signed in to another service-So from zimbra you could send mail as
user@gmail.com without switching clients/browsers/etc.
However that would only take care of sending, you would need an
alias to receive mail at
first.m.last@domain.com or
first.last@domain.com.
You can have some interesting setup's domain wide as well:
ManagingDomains - ZimbraWiki