Who's your email address through? Hotmail, Yahoo, your ISP?
I'm on Roadrunner and I can check all my mail addresses fine with Mailwasher. I also have a couple of yahoo and hotmail addys, but for them, I use PopPeeper. It works great and they are on the ball with fixes everytime hotmail or yahoo change their protocols. It also supports many other email providers.http://poppeeper.com/
Now, I don't do anything else with them. Like answer my mail through them. I just use them to look-see and delete what I don't want to download when I open Outlook Express to get my mail.
I do have an older version of Mailwasher and sometimes it does burp when checking all four accounts at once. I will get a message box saying it couldn't access one account and possibly because of firewall settings. When it does that, I just go back up to the menu and select the individual account that Mailwasher is complaining about and tell it to do it again. Then it works.