Which mail server is best suited for my tasks (AD, IMAP\MAPI)?

Question

Active Directory

Good afternoon!
I have finally matured to make a mail server, I want it to do the following.
1. Stored all the mail and conveniently (automatically) backed up / restored the database.
2. Was "intermediate" - i.e. would receive\send mail through the hoster via POP3\IMAP, but if the hoster fails, it would work independently (MX-records?).
3. There are several dozen boxes on the host, several dozen users, one box is often registered on more than one user (sometimes for all users). All users in AD, Outlook 2013 clients. I would like to register on the mail server from which addresses this user receives mail and to which folders, and authorization in Outlook would be minimal, by username in the domain, for example. Accordingly, work with clients takes place via IMAP\MAPI.
4. Configuration via GUI.
5. Free is not required.
I tried Exchange, but in order to simply receive mail via POP3, some left connectors are needed, there was no time, and I abandoned this business, or maybe in vain.

Answer 1

Kerio Connect. Not free, but good functionality and easy initial setup and administration.