My issues with Exchange? Let's see:
- it's an overblown, over-engineered piece of shit designed to give "IT managers" and their secretaties a boner and suck them into Microsoft's vendor lock-in hellish groupware who still thinks we're in the 90s (fuck sharepoint, too while we're at it!)
- requires big resources to work faster than a snail (fuck sharepoint again!)
- to deploy it you need to also deploy more microsoft dinosaurs such as AD 2020 with CRAPFIX 9887622 running on Windows NonStandard Edition SP4 (no less!)
- to use more than 10 mailboxes you need a cluster of 10 microsoft certified hardware servers, double it if you want it in 64bit
- the webmail interface (which I had been forced to use in the past because I was using Linux) is ridiculous usability wise, sluggish, multi-message operations are very slow, the filters are a joke compared to procmail or maildrop; .forward does not exist
- some poor bastards confuse it with a proper MTA and leave it facing the internetz directly, most serious deployments I've seen run a nix based installation (qmail, postfix) in front of it and firewall the hell out of it because you can't have it exposed to a network
- sometimes when it breaks not even highly microsoft trained monkeys can fix it unless they sacrifice a couple of chickens to the voodoo gods
- if you want to count on certain mail standards (other than Microsoft's that is) you're pretty much on your own: imap support is shit, exporting to anything other that random m$ tech is not supported
The list could go on and on. That's what I think of Microsoft's "reliable software".
Needless to say, I'll pick e.g. Thunderbird any day over it, although I'm using more and more console based clients nowadays (such as cone or lumail).