OS X iCloud Outgoing Server

I have a 5 month old new version of the Mac Mini running all the latest software and updates. On my Mac, I can not send any outgoing emails, it just gets stuck in the outbox and comes up with the select server option. I have tried entering new server details in but when I enter the apple ones it just forgets them and disappears from the list, I have also tried other ISP outgoing server details but it won't work. When I try the connection doctor it states that it can connect and log in.

The only major change from when it did work and when it stopped is when we moved from the UK to Germany. So again I have tried the T-Mobile (our ISP) server details as mentioned above, though this doesn't seem to work. Also my iPhone doesn't seem to have a problem sending emails with the same account through the ISP.

I have also tried disabling the mail in the iCloud settings, rebooting the computer and resetting up the mail account. this didn't work. Last resort is reformatting the whole computer but surely this is over the top and too time consuming for a bug like this?

I am lost on what else I can try to do now? Help please!