The -b option causes smtpsend to enter infinite loop of scanning mail\out folder and send detected messages out. You have either to remove thie option or to add -z option that prevents running of more than one copy of smtpsend.

Also, you have an error in the -pop option. If you're really need to use POP authentication before SMTP sending use the following format:
-pop %Server% %Login% %Password%
If you need to use SMTP authentication use -w option instead of -pop to indicate your password.