Which mail client (Windows) is best for corporate mail?

Question

Windows

Hello.
We have been using Microsoft Outlook 2013 for three years to work with corporate mailboxes. More than 10,000 letters are spinning on the boxes, and up to 20 accounts are on the clients themselves. Unfortunately, anomalous situations occur with Outlook - sometimes endless synchronization comes with a stupid clogging of traffic, then letters appear two years ago with new dates, then all letters disappear from the client at one fine moment. In general, I'm already tired of this whole thing, I would like to try alternative mail clients. Email clients connect to IMAP servers using the SSL protocol.
Important: ease of use, backup, normal work with IMAP.
Thank you.

Answer 1

We use TheBat at work!
This client processes emails (a letter arrives from the desired recipient + subject + extension, then it is placed in the desired mail folder, the status changes to read and launches vbs).
There are no special problems with it, I find it difficult to name its analogue, from free ones (and thebat costs money), probably not.

Answer 2

Everything that you listed works quietly with the MS Exchange 2013 server, I confirm that Outlook itself does not work very stably with imap when using other servers. If you have everything licensed, then why not use Microsoft products for the server as well.