One e-mail address not working

I have two e-mail addresses. They were both working fine until yesterday. Now it says that either my password or settings is not allowing it to connect with one of the e-mail addresses, and we never changed anything. I tried getting my ISP to work it out. We even reset the password. I can do the e-mail through their site, which isn’t very good, but not through eM client. Any idea why?

I’m having the same sort of problem, I have 4 email addresses & on 2 of them it keeps saying my password or settings are wrong, very frustrating!