I get this little squiggle next to Mailbox and can't fix

I have a business address and a personal. I dumped Apple mail last year because it kept on crashing and switched to OUtlook which is worse. Got Outlook for the calendar so I can make appts with clients. ical isn't compatbile with MS- wish Apple would make it so. But so many Outlook probs so now back to Mail but not sure if I'll be happier. But.....

I am trying to just grab this account. I never disconnected from mail but for some reason, one account can"t seem to work. It is a POP account. I have checked settings with ISP provider and it seems fine. But it is always offline. I have searched and scoured the net for answers and don't know what to do. It's not that complicated so I dont know what the fix might be. Hoping someone can help. Running Snow Leopard. Thanks