He meant it as a features.
If someone that I do not know is mailing me, i rather it cost them an arm and a leg because I know more than anything, it will likely be junk mails. I only want mail from friends, guildmates, systems, and GMs/GSs.
Same for whisper, I only like to have whisper from people on my friend list, guildmates, etc. This also include temporary whisper from party members as well.
Common Used IGN: Kyuusho, Keima, Miai, Eternia, Agranite