While yes, the move to only allow you to mail people on your friend list was to prevent muling, it wasn't to force you into subscribing retainers. Subcription retainers wasn't a thing till months after 2.0 launched. It's intended to inconvenience RMT. XI muling was heavily used to launder gil as for the longest time there wasn't much of a limit on what you could mail outside of RA/EX items, nor to who as you manually wrote the name of who you were mailing. Understandably, RMT abused the hell out of that, millions of gil just circulating around like it's nobody's business. In this game they are trying to curb that with the mail system. I don't mind, really, but I never used mules in XI either. I had better things to spend $12 on than a character I'd never really use.