Outgoing Mail Server Offline

Hey guys,

here Mail is driving me crazy... I configured it once but from time to time when for example I move from home in the office I have problems in sending emails. It says that the outgoing mail server is offline. Actually at a certain point it starts to work again but I've no clue what was wrong. I try to change settings but then I but them back as originally and magically it works again but is not alway the case.

I'm a scientist and I don't like very much this Magic... It simply should work as expected. With Tiger I did not have a single problem with Mail...

Any idea!?