In reply to a post by MakeMosaicTrace:

I used 'relay.o2broadband.co.uk' as the smtp, authenticated with my o2 password.

There is no reason then for this not to work as well in the Mac Mail client, whatever that is, that you first tried.

Any reason why you used 'relay.o2broadband.co.uk' rather than 'smtp.o2.co.uk' given in that link of AEP's?

You should be able to also receive from your homecall address by using the homecall/pipex POP3 server as the Incoming.