Mail issues

Hi, this problem has got me more than confused!

I am using an iPad and iPhone both running iOS 6 and a Acer Netbook running Windows 7.

The email addresses I am using are custom domains from Bell with the incoming mail server being pop.bellnet.ca and the outgoing smtp.bellnet.ca

All devices can recieve emails but cannot send. And the part that confuses me the most is that they can all send and recieve on our office wifi but at any other location they will not send.

Hoping someone out there has some ideas!

Thanks!

Gemma