I'm not a legal professional, but will try to answer your question. It's really sad that this 'friend' has cheated you. The fastest way to lose a friend is to lend them money.
Email evidence is considered as evidence in many countries - many famous cases have been settled on email evidence (Bill Gates lost in the Microsoft Anti-Trust case on email evidence). Since you have his work Id, it will be easier for you to show that the Id belongs to your friend and the person answering it was your friend. The server details (physical location of the email server, etc) and the user's IP (showing which internet service this user was using and what was the user's approximate location) can also be traced from the server records.
How did you lend the money? Hopefully by cheque and in your friend;s name? If you paid by cash, it's harder to track the crook down. Cheque payment is undeniable evidence that the money was lent.
Now that being said, the bad news. Our courts, as you might know, require some physical address to serve notice and summons. It might not be so hard to trace your friend if you do some detective work, or hire a Private Investigator. Ask his relatives, friends, former colleagues, landlord, old neighbors, his bankers (banks usually have permanent address and they might do you a favour), visit the school where his kids (if any) used to study, track down anybody he used to know and ask. A detective might also help you gather more evidence.
Frankly, even when you DO have the address our courts are a pain in the behind. The overall intelligence of people in the 'system' bailiffs, policemen, clerks, judges...oh, the less I say about that the better, not to mention their lack of integrity. For every small thing such as service of summons, you have to bribe. And the COURT FEES - Frankly, for your court fee money you can hire a good private eye (detective) who will track down the fellow. They will charge less than a lawyer any day. Don't waste your life filing a lawsuit but do threaten the person with a lawsuit.
Track that fellow down, confront him with the evidence and threaten him of dire consequences. Hopefully this person will pay you back.