There are several ways that spam can bypass or fail to delete in mailwasher...
1.) Ensure that these emails are in the inbox folder in your email program when they arrive, (MWPro can only see the inbox folder for POP3 type accounts)
if they are in other folders on your ISP's mail server, MW wont be able to show you these unless you set up the account as a IMAP type in MWPro, (if your ISP supports this).
2.) Ensure that your email client is not set to check for mail every XX mins therefore bypassing MWpro, checkout the below link for details on how to disable this:
3.) Click View>>Show hidden emails, as possibly one of the spam tools within MW is hiding these emails.
4.) Ensure you don't have an email account setup in your email client that the mail check is not checking in MW.
(In MW check your accounts are being checked under Settings>>Accounts, click the account>>Incoming tab, ensure that, "Include in default mail check" is ticked)
5.) Ensure that the delete box IS ticked for the emails you want deleted before you click Wash Mail in MWpro.
6.) Try closing Mailwasher completely after Washing mail, wait a minute, and then open your email client and check mail.
(You will have to uncheck, Settings>>General>>Washing Mail, "Launch email application after wash mail" and click OK there first)