Can't send emails unless connected to home wifi

[DenisParkes]

Please help. Samsung Galaxy S. 2 email accounts. The (mandatory) googlemail one and my proper one which at home I view through MS outlook 2010. I can read all emails and send replies and news when at home and connected to my home wifi. I could originally also send emails over 3g when out and about or if connecting to a wifi hotspot. But this has now stopped and all outgoing emails just get stuck in my outbox no matter what I do.... until I come home and connect to my home wifi (and only my home wi-fi). Any ideas why, and more importantly what I need to do? (Message says can't connect to server)