because when you mail items between legacy characters, it creates lag.
Can't say I've noticed this, and I send mail between Republic & Imperial toons often. Just how does sending mail between my toons create lag? Do you mean server lag? Because, I don't see much of that, either. I see a lag spike or two on the weekends, due to heavy internet traffic all over North America, but I fail to see how eliminating inter-toon mail will help ease the burden of continental weekend internet traffic.