Cannot open Mail.app Preferences in OS X 10.7.5
You can reset Mail's settings by running the following one-liner in Terminal:

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


https://georgegarside.com/o/se/reset-osx-mail.html