In order to solve your problem, you need to delete some files from your Library folder. If you don't know how to view the Library folder, you can simply use Google to find an answer depending on your OS version. In order to fix the Mail application, you need to delete the following files :
com.apple.AddressBook
AddressBook-v22.abcddb
com.apple.preferencepanes.cache
After you delete these files, simply restart the computer and the application should work normally. However, for more info about this problem, you can visit the following forum or forum.