Ah but the solution was an X.500 directory where you just look up the recipient! So you never type the e-mail address, you just look up "Joe Smith" to send them an e-mail. Like looking them up in the phone book. Ignore the fact that the directory may return multiple Joe Smiths at the same large organization, not return Joe Smyth you wanted to message, or that there's not even a hint of anonymity with such directories. Oh yeah the internal organization of a company could be easily enumerated from the outside.