I can send but not receive emails

My clients are using outlook express. And 2 out of 5 clients outlook express is funtioning correctly. However, i called Verio(the web hosting company) and they said they will get back to me.
It was confusing b/c i would create new addresses, but it would reply back that the password is incorrect. This is even after i created new accounts and entered the password myself. These are window 98 clients.

Thank You

Tigger