1.) Third party mail client: I am not sure if there is a specific setting to allow/disallow, but as long as I authenticate I am able to define ANY sender in my mail application setup.
2.) Zimbra mail client (website): Make sure you did define an alias for the user, then login as such to your account and select add a new identy in Preferences->Mail->Accounts selecting the alias. Now select the idendity when creating a new mail... Or simply change the primary identity. |