We use the template for mail in db's.
We have cleaned out templates also (less preferences), just for use as mail inbox for a project, or another one to use as project mail inbox with mail rules, .....
From what I have noticed :
- The new mail reminder works as expected when new mail arrives in the inbox (we use it in some of them)
Under Mailbox preferences you have the tab new mail reminder, where you can set the people who need to receive (and other things) and the button to enable the feature
- The mails sent from the mailbox if configured correctly carry a mail address of choice (best to use the one from the mailbox)
Under Mailbox preferences you have the tab advanced, here you can set the mail address for example
Don't have used or saw the empty trash feature, but the default in db props stands at 336 hours :-) to empty trash, as for a standard mail file it stands at 48 hours.