Accounts are ALWAYS recoverable, even with a Middleman/Recovery Test!

Account exchanges with a middleman

Always be cautious with account trades, even if you are using a middleman. Remember, accounts can always be recovered, so even if the trade goes smoothly, there's nothing stopping the original owner from recovering the account down the track, leaving you out of pocket, and without an account.

Do not be lulled into a false sense of security.
Using a middleman does not eliminate the chance of you being scammed, because the account can still be recovered.

We recommend that you always proceed with caution when you are buying accounts, even with a middleman.
We also strongly advise you to take all screenshots of the trade, and refer to this sticky for the evidence required.
This will ensure that if your account does get recovered, we can ban the person to prevent others from being scammed.

Further Reading: http://www.sythe.org/threads/accounts-are-always-recoverable.1247771/

Recovery Tests Do NOT Ensure Safety

Many customers will purchase an account and perform a recovery test, and his decision of buying the account depends on the results of a "recovery test." These practices are utterly pointless. Yes, a recovery can tell you if the person is lying about the information or not--however, BY FAR the most important thing in a recovery is the computer from which it is performed.

Performing a recovery test does not ensure that you, the buyer, will not be scammed. After you buy the account, there is a very easy method for the original owner of an account to "lock in" the IP address so that only his own computer can perform a recovery. DO NOT think that an account is safe to buy simply because it passes a recovery test! Please consider all factors in a trade (such as the seller's background, the chance you think he would scam you, etc.) before buying!

Credit: KerokeroCola