tawhwat When a user composing a new mail (or reply, forward a mail), the "From" field is restricted to only choose the email address from the Address book. Is there any switch to change its behaviour to allow the users to type the address instead of popping up the address book?
I don't think this will ever be implemented. If it's not in the global addressbook the mail isn't managed by this system and so it will fail as you most likely can't receive a answer or even a mail delivery report.
tawhwat Furthermore, Is there any way to allow users to send-as whatever address (typed at the "From" field, even for the address not existing in the address book) without checking their permission? I understand that may impose security issue as the users can masquerade any person, but I would like to accept this risk.
No.
Grommunio is not meant to do things you shouldn't do with E-Mail. Of course if you also enable a catch-all so every adress you come up with will also be reachable it might be considered not as a total f*up (forgive my french). But as long as you won't come up with the code changes yourself i honestly don't believe such a thing would ever be added to Grommunio. And even if you created such a patch i still don't think they will merge it.
Sure, if you use imap/pop3+smtp than you can do pretty much do whatever you like but thats it because outgoing mails will go through postfix and unless there is any "guard" to test if the adress even exists and/or your user (if you even use authentication) is allowed to use this address it will not stand in your way.
