upgraded to OSX Yosemite 10.10.1 (14B25) had nothing but problems with Mail. One site suggest deleting V2 folder in the Library/Mail folder. I did so with the understanding that I would have to reregister my accounts. Each time I try to setup my google account, typing in the account name and password, when I press setup those fields are blanked out and I can go no further. When I click cancel the whole Mail.app quits.. What can I do to restore Mail.app to some form of usefulness????