Let's say I bought gold, and let's say I received this e-mail within 12 hours after doing so: How, if I want to buy more gold, do I avoid this? To compare, the account I used for buying LOTS of gold a year ago, still works, never got a notice or something else.
This is automatic notification and afaik does not do any impact on your account, ye it sucks to get this kind of letter sucks to know blizzard knows it all, but who cares if does not affect you in any way. If their server script somehow detects in-game gold trade (any in-game gold move actually including AH and GB) was RMT-related than it a) bans "seller" with default eco-ban b) sends "buyer" this kind of letter. And again its not even because of RMT, they ban seller in effort to protect the account in case it was stolen, not purely because of RMT factor. They really dont hate RMT as much as you may think, its all about black stolen gold. Oh and yea, if the gold you got was indeed "bad" (stolen lets says and original owner claimed it) they can "remove" it from you. But thats another story.