outgoing mail server says it is off line works fine on desktop and ipad but not laptop

I am having problmes getting my outgong email to work on my laptop. The account settings work fine on the desktop and the Ipad but not on the lap top. I get the message that the outgoing server is offline. I have deleated the account and set it up again stil getting the same message. Does anyone have any ideals on how to correct this?