[IMPORTANT] If you're using catchalls, update SER to the latest version because...
Hinkys
SEOSpartans.com - Catchalls for SER - 30 Day Free Trial
There's was a bug in SER (fixed in version 10.95) where if you used the same catchall in 2 or more projects with "delete message when verification link found" option enabled, that option would basically behave as "Delete ALL messages", effectively lowering your number of verified accounts. (which results in less verified links than you'd expect).
This problem has been fixed by awesome Sven in 10.95 so please MAKE SURE that you update SER to the latest version.
Optionally if you must keep using an older SER version for whatever reason, just disable "delete message when verification link found" in all your projects. You can do this in all projects at once by selecting all of them, right click -> edit single options for all -> pop3 del message -> 0