It must be something to do with the rules you`ve set up. Check them carefully and look for the words and symbols in the friends e-mails that were sent to the bin.
Personally I use Mailwasher Free click here Set up Outlook to "Leave a copy on server" and use Mailwasher to interrogate your mail server. Delete any obvious spam mails and designate others as "friends" for future reference. Once you have the e-mails safely in Outlook, delete them from mailwasher. One word of warning - don`t bounce any, you`ll just get more spam. Simply blacklist the sender & delete them.