I always thought that not being able to send mails to my other chars was some technical limitation. Now that I read that it is technically possible, I find this even more absurd (yes, you could only befriend your alts through a glitch years ago - but obviously having alts on your friend list does not set the servers on fire, so technically it's possible).

And no, one char is definitely not enough - I currently have 14 chars, which I all play whenever the mood strikes me.