ugh.book

74 Mail

some non-standard environment variable set so he couldn’t use

Emacs or vi or any other screen editor so he couldn’t see there was

an extra blank line that Unix would rather choke dead on than skip

over. That’s why.

From: [email protected] ...........................

The problem with sendmail is that the sendmail configuration file is a

rule-based expert system, but the world of e-mail is not logical, and

sendmail configuration editors are not experts.

—David Waitzman, BBN

Beyond blowing established mail delivery protocols, Unix has invented

newer, more up-to-date methods for ensuring that mail doesn’t get to its

intended destination, such as mail forwarding.

Suppose that you have changed your home residence and want your mail

forwarded automatically by the post office. The rational method is the

method used now: you send a message to your local postmaster, who main-

tains a centralized database. When the postmaster receives mail for you, he

slaps the new address on it and sends it on its way to its new home.

There’s another, less robust method for rerouting mail: put a message near

your mailbox indicating your new address. When your mailman sees the

message, he doesn’t put your mail in your mailbox. Instead, he slaps the

new address on it and takes it back to the post office. Every time.

The flaws in this approach are obvious. For one, there’s lots of extra over-

head. But, more importantly, your mailman may not always see the mes-

sage—maybe it’s raining, maybe someone’s trash cans are in front of it,

maybe he’s in a rush. When this happens, he misdelivers your mail into

your old mailbox, and you never see it again unless you drive back to check

or a neighbor checks for you.

Now, we’re not inventing this stupider method: Unix did. They call that

note near your mailbox a.forward file. And it frequently happens, espe-

cially in these distributed days in which we live, that the mailer misses the

forwarding note and dumps your mail where you don’t want it.

(^3) “Ed is the standard Unix editor.” —Unix documentation (circa 1994).