cannot delete emails

For several months, I have not been able to delete emails, and I can't seem to ignore the problems any longer :-)

 

When I try to delete an email after reading it, whether by clicking on the "delete" in the email, or right clicking "delete", or even trying to move it to the deleted items folder, I get a pop-up box telling me the "message cannot be deleted".  Then when I try to get rid of the pop-up box (by clicking either "x" or "OK"), it just reappears.  Then I'll click "x" again and then it disappears.

 

I have been to the "deleted items" folder to try to determine when I was last able to successfully delete something, but it was empty (although I hadn't emptied it.)

 

Around the same time this problem started, I also started getting a lot more spam then usual, if that's any help.

 

Using Roadrunner, Windows XP Home and Outlook Express 6.  Thanks for any help!