How can I delete my Mail App and re-install it?
Before you delete it, see if you can repair Mail.


In Mail, go to Window → Connection Doctor and let it verify your connections to see if all works there.
Next step is to rebuild your Mail database. Go to the Mailbox tab and at the bottom click on Rebuild.

If 1 and 2 are not accessible (grayed out)
Try to reset Mail settings. - which you will need to set up after following:

Quit Mail, then go to Finder and press ⇧⌘G and enter (or copy) the following:

~/Library/Containers/com.apple.mail/Data/Library/Preferences


Look for "com.apple.mail.plist" and drag it the Desktop, then restart Mail.


Alternatively, you can use this one-liner in your Terminal app (located in the Utility folder):

killall Mail &amp;&gt; /dev/null; mv ~/Library/Containers/com.apple.mail/Data/Library/Preferences/com.apple.mail.plist ~/Desktop &amp;&amp; open -a Mail


Source: http://georgegarside.com/o/se/resetMail.html



If all else fails you can reinstall the operating system (Mavericks) that includes the Mail.app. Boot into the Recovery HD with ⌘R, then follow the instructions.

For more information about recovering a broken Mail.app, see this:


http://www.techrepublic.com/blog/apple-in-the-enterprise/how-to-recover-email-from-apple-mail-corruption/


You can check if a 3rd party app/extension is causing the problem by performing a safe boot (hold shift on boot).

In rare occasions your user permissions or ACLs might need some repair. This answer describes the process.