Hi.
We intent to replace exchange server 2013 with the best alternative running on linux. Why?, due to hight cost, but, we plan to migrate dekstops step by step and it means we need to maintain some outlook clients an evolution or thunderbird working in parallel, i mean 50 desktops with evolution, 400 with outlook.

We do not have any complex functionality just exchange and SAP, plus other medium apps that not impact Email.

So, could you advise please?

Kind regards

Welcome to LQ,
I would suggest to take a look at zimbra.
There are 2 versions, the opensource (free) and the network edition (paid), so you can use the one that fits your needs.

Regards

There's also OpenChange to look at. I expect the main priority would be to get the server OS itself off of M$ and onto something stable. I'd use an LTS distro for that so that you have at least a few years between migrations.

If you are NOT migrating your desktops to Linux, you should know that MS OUTLOOK does support other mail systems than Exchange: It is IMAP compatible. If you are not using or wish not to continue running MS Outlook (Which is clearly not inexpensive to install or upgrade) then migrating to an alternate email client makes very good sense.

There is absolutely nothing to prevent you from running multiple email clients on the same workstation. Each may be pointed to only one, or to EVERY one, of your email servers.

FYI: Exchange, with the task, email, calendar, contacts integration IS a complex functionality operation. Exchange does FAR more than just email. Look for the most integrated and complete replacements if you require those features.