Do Vodafone have anything to say about the matter (server problems, etc.)?
Mail usually does a good job of setting itself up if you give it the basic settings (your email address, password). You can check these settings in Mail>Preferences>Accounts (vodafone is a pop account).
Mine works fine with the following
Incoming mail server = pop.vodafone.ie
Outgoing mail server = mail.vodafone.ie
Did you use migration assistant to move from another machine recently? It sometimes does strange things with server addresses.