Every time I try to launch Mail with an Exchange account, it crashes and logs an error about a Root Folder ID:
6/11/15 11:58:30.328 AM Mail[711]: Root Folder Id changed from AAMkADE2NTQ2MmEzLWM5MTktNGRhZi04Y2VjLTc5OTBmYjYzYzgwNwAuAAAAAAB36UObOHIYTYg15OKpUhYCAQBxk81w29aJSJP4PRGq7mb6AAAAAX/sAAA= to AAMkADE2NTQ2MmEzLWM5MTktNGRhZi04Y2VjLTc5OTBmYjYzYzgwNwAuAAAAAAB36UObOHIYTYg15OKpUhYCAQBxk81w29aJSJP4PRGq7mb6AAAAAX/rAAA=: once an account is created, the root folder id shouldn't change on the server
If I disable Exchange mail from the Internet Accounts system preference, it launches.