Create an account for the "virtual" address,
foo@domain.com.
Then share the Inbox and Sent box for that account to all the people who will be "sharing" the "virtual" address.
Have each of the shared users create a Persona that sets the From/Reply-To to the virtual address, and check the box for "Use for all mail in this folder", setting it to the shared inbox.
After that, any mail sent to
foo@domain.com will go to the foo account. All the shared users will see the mail in the shared "Foo's Inbox" folder. When they reply to messages in that folder, it will automatically set the From: header to
foo@domain.com. For new messages, they just have to select the
foo@domain.com persona.
We use this for our Helpdesk.
helpdesk@domain.com is a resource account, shared out to 6 people. Each of those 6 people has a Persona configure for the
helpdesk@domain.com address.
There are a couple downsides to this method:
* tags are not shared correctly, so you really should avoid using tags for the shared mailbox
* replies are put into your personal Sent folder, and are not incorporated into conversation view of the shared mailbox (you have to manually copy sent messages to the shared mailbox)
* the first person to read a message marks it read for everyone, so it's possible for messages to get missed by some people (per-user read status is missing)
However, once you understand those shortcomings, things are workable.