cannot retrieve my mail

I keep getting asked for my pw when trying to send or retrieve my mail.

No matter how many times I enter it, it continues to ask.

I also replaced and saved it in the preferences.

I compared the mail preference between 2 iMacs I own.

I discovered that on this iMac in mail preferences the out going mail server

reads “Verizon (Offline)”

How can I change this to on?

Mac Yosemite OS.

I’ve performed a complete backup from the working iMac

but, still encounter the same problem.

Thanks for your help.