After upgrading Macbook Pro, iMac from Mavericks to OS X Yosemite, Mail app crash or hang when users open it and it preventing user from accessing new messages.
Solution 1:- (Launch Mail app in Safe Mode)
When you launch mail, the application shows the last mail that you had selected with errors, that error causing the crash issue.
If you want to fix this issue, open mail app and immediately hold down SHIFT key until the program opened.
Solution 2:- (Start your Mac into Safe Mode and open Mail app)
- Restart your Computer.
- Hold down Shift key when you hear boot sound. This will launch your operating system in Safe mode.
- Launch mail app in Mac Safe mode.
Solution 3:- (Delete mail save state)
Mac OS X Yosemite will save open or running programs window locations. Its automatically reopen programs in next relaunch (computer restart).
So remove the mail saved state and relaunch the Mail app.
- Open Finder.
- Press and hold the Option key and then navigate Library from the Go menu.
- Navigate to Containers -> com.apple.mail -> Data -> Library -> Save Application State folder.
- Find and remove the folder named com.apple.mail.savedState.
- Re-open Mail app.
Solution 4:- (Temporary disable Mail accounts)
- Go to Mac System Preferences -> Internet Accounts and uncheck the mail option for each account.
- Then reopen the mail app and check it it launch correctly.
- Then quit the mail app and re-enable the mail accounts.
SEE ALSO : Mac Mail not showing new messages in inbox, fix
Solution 5:- (Move V2 folder)
Move your V2 folder to Desktop (located in /library/mail/v2) and relaunch your Mail app.
Solution 6:- (Delete and Re-add Address Book folder)
Open the Go menu in Finder, then press and hold Option key when Library option appear. Select that option and go to Application Support Folder. Delete Address book folder from Application Support and re-build contacts in Address book.
- Remove old IMAP folders within the Library -> Mail -> etc.
- Disable Yahoo account and check your issue.
- If you installed any 3rd party Mail based apps like password managers, junk mail filter and security software for encrypting mails, uninstall them.
Go to Library -> Mail -> Bundles folder and delete any items in it.
- Turn off all user restriction rules.
- Delete and re-add you exchange account information in Internet accounts.
If you have any other problems or solutions, inform us via comment.