I've had several discussions with different GMs, pretty much all of them told me to transfer larger sums of gold via ingame mail, and they told me to avoid transfering tooooo much at once. I always used 50k chunks, and never received a ban, not even a temp one.
Oh, and I got reported a lot for gold selling/botting, cause I've been in full control of my servers gem market for several years. None of my gold ever left my accounts though, not even to random friends. When I've quit playing and handed large amounts of gems to some friend of mine, I reported myself, explaining why I'm mailing stuff worth 100k+ to someone else. The usual GM answer: "no worries"...