Fixed bug which appeared on first past through notification email.

git-svn-id: https://plugins.svn.wordpress.org/email-users/trunk@946267 b8457f37-d9ea-0310-8a92-e5e31aec5664
Added before and after wp_mail hooks.

git-svn-id: https://plugins.svn.wordpress.org/email-users/trunk@946268 b8457f37-d9ea-0310-8a92-e5e31aec5664
Prep for 4.6.10 release.

git-svn-id: https://plugins.svn.wordpress.org/email-users/trunk@946269 b8457f37-d9ea-0310-8a92-e5e31aec5664