Certainly doable PG - easiest way would be to give your contact a bell (if you know their number) and ask them for their external address. Everyone with a DII account has two e-mail addresses: one linked to the post they occupy and a personal one. The personal one takes the form "email@example.com" and the post one will be along the lines of "post title"@mod.uk
But you need to have an IGS account. If you have access to the internet from DII then you have an IGS account.
Generally you get two e-mail accounts your DII one which is set to your appointment or job
Tp Comd 4 troop b coy 4 btn blankshire
and your IGS one which is linked to you personally
Surname first initial and 3 numbers (Atkinst123)
in each case the e-mail address will end in .mod.uk or @mod.uk. dependant upon your unit set up. The best way of finding out your full mil e-mail is either look yourself up in the global address list and find the e-mail under properties or
send an e-mail to your private civy e-mail address not forgetting to start the subject heading with Release-authorised:......