I decided I was tired of having 2-3 tabs open for my different email accounts and having to deal with the office 365 UI... so I setup Mail on my Mac. The performance was really bad at the first and it crashed a few times when setting up the accounts. I thought it might be because of the 5000+ emails I had so I started cleaning up! Got it down to less than 300 (thanks to the rules it didn't took that long.). I was starting to get used to the UI and was enjoying it until I needed to send my first email... Trying to attach a small excel file froze the app and I had to force quit and restart. It worked the second time. Anyway, overall the experience has been pretty bad. Never experienced anything like this with the web clients or with Outlook. I'll keep using it for some time and hope it gets better. My Mac is getting old (2011 15" MPB) and I plan to replace it soon but no other apps I use have issues like that. It's an email client, it really shouldn't be too demanding. Any Mail users experiencing similar issues? Is there something I'm doing wrong? Or am I just unlucky and it will get better?