66 Mail three pictures, and he picked the bat because it appealed to him the most. The fun answer is that, although sendmail has a reputation for being scary, like a bat, it is really a rather friendly and intelligent beast. Friendly and intelligent? Feh. I can come up with tons of better answers to that one. Especially because it’s so patently wrong. To wit: • The common North American brown bat’s diet is composed princi- pally of bugs. Sendmail is a software package which is composed principally of bugs. • Sendmail and bats both suck. • Sendmail maintainers and bats both tend to be nocturnal creatures, making “eep eep” noises which are incomprehensible to the average person. • Have you ever watched a bat fly? Have you ever watched Sendmail process a queue full of undelivered mail? QED. • Sendmail and bats both die quickly when kept in captivity. • Bat guano is a good source of potassium nitrate, a principal ingredi- ent in things that blow up in your face. Like Sendmail. • Both bats and sendmail are held in low esteem by the general public. • Bats require magical rituals involving crosses and garlic to get them to do what you want. Sendmail likewise requires mystical incanta- tions such as: R$+$*$=Y$~A$* $:$1$2$3?$4$5 Mark user portion. R$+$*!$+,$*?$+ $1$2!$3!$4?$5 is inferior to @ R$+$+,$*?$+ $1$2:$3?$4 Change src rte to % path R$+:$+ $1,$2 Change % to @ for immed. domain R$=X$-.UUCP!?$+ $@$1$2.UUCP!$3 Return UUCP R$=X$-!?$+ $@$1$2!$3 Return unqualified R$+$+?$+ $1$2$3 Remove '?' R$+.$+$=Y$+ $@$1.$2,$4 Change do user@domain

Subject: Returned Mail: User Unknown 67 • Farmers consider bats their friends because of the insects they eat. Farmers consider Sendmail their friend because it gets more college- educated people interested in subsistence farming as a career. I could go on and on, but I think you get the idea. Stay tuned for the .22 penetration test results! —Rob Subject: Returned Mail: User Unknown A mail system must perform the following relatively simple tasks each time it receives a message in order to deliver that message to the intended reciepient: 1. Figure out which part of the message is the address and which part is the body. 2. Decompose the address into two parts: a name and a host (much as the U.S. Postal System decomposes addresses into a name, a street+number, and town+state.) 3. If the destination host isn’t you, send the message to the specified host.