I have been using OS X Mail for quite a while and I had it always working with 4 different email accounts: Gmail, Hotmail, Exchange and another one. Ever since I updated to El Capitan, Mail keeps crashing with the "Mail quit unexpectedly" message every time I try to work with my Exchange account. Just by clicking on a message (one single click to preview it) from the Exchange account Mail will quit. It is the email account provided by my workplace, so I cannot get rid of it. I have tried removing/deleting the account from the Mail Accounts Preference Menu and have added it again. I have tried to close Mail and even reboot the system, but the problem persists. As a workaround I am using the Exchange webmail version, but I would love go back to using the Mail account... Apple might fix it on their next OSX update, but it's not for sure and who knows when. Meanwhile, any help would be appreciated! I am really desperate! Thanks in advance!