I installed Yosemite and my mail is always crashing

Question

I get this as error
Process:               Mail [2960]
Path:                  /Applications/Mail.app/Contents/MacOS/Mail
Identifier:            com.apple.mail
Version:               8.0 (1990.1)
Build Info:            Mail-1990001000000000~3
Code Type:             X86-64 (Native)
Parent Process:        ??? [1]
Responsible:           Mail [2960]
User ID:               501
Date/Time:             2014-10-27 15:40:37.242 -0400
OS Version:            Mac OS X 10.10 (14A389)
Report Version:        11
Anonymous UUID:        F913F4B4-2339-0644-3E45-9B352162B455
Sleep/Wake UUID:       7747363C-CCC1-423D-BBAD-1683CD886B94
Time Awake Since Boot: 41000 seconds
Time Since Wake:       67 seconds
Crashed Thread:        30  Dispatch queue: NSOperationQueue 0x6080002deae0 :: NSOperation 0x6080002d0450 (QOS: LEGACY)
Exception Type:        EXC_CRASH (SIGABRT)
Exception Codes:       0x0000000000000000, 0x0000000000000000
Application Specific Information:
*** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'Require mailbox name to create IMAPMailbox for (null)'
abort() called
terminating with uncaught exception of type NSException
ETC.........
why is this happening.....

Answer 1

Reinstall Lion, Mountain Lion, Mavericks or Yosemite without erasing drive
Boot to the Recovery HD:
Restart the computer and after the chime press and hold down the COMMAND and R keys until the menu screen appears. Alternatively, restart the computer and after the chime press and hold down the OPTION key until the boot manager screen appears. Select the Recovery HD and click on the downward pointing arrow button.
Repair
When the recovery menu appears select Disk Utility. After DU loads select your hard drive entry (mfgr.'s ID and drive size) from the the left side list.  In the DU status area you will see an entry for the S.M.A.R.T. status of the hard drive.  If it does not say "Verified" then the hard drive is failing or failed. (SMART status is not reported on external Firewire or USB drives.) If the drive is "Verified" then select your OS X volume from the list on the left (sub-entry below the drive entry,) click on the First Aid tab, then click on the Repair Disk button. If DU reports any errors that have been fixed, then re-run Repair Disk until no errors are reported. If no errors are reported then click on the Repair Permissions button. When the process is completed, then quit DU and return to the main menu.
Reinstall Lion, Mountain Lion, Mavericks, or Yosemite
Select Reinstall OS X from the main menu then click on the Continue button.
     Note: You will need an active Internet connection. I suggest using Ethernet
                 if possible because it is three times faster than wireless.