Some files contain lines that begin with
the five characters "
From " (the fifth character is a space).
What happens to such lines when the files containing them are delivered
to a local mailbox?
What UNIX utilities
are available to aid in sending such a file with those lines
In the file sendstuff, we created a one-line header that
Subject:. What would be the effect of making
that header all lowercase? What does RFC822
have to say about this?
(See "Additional Sources of Information" in
How does sendmail behave when it is given a message that contains only a header? Does it add a blank line to create an empty body?
If your MUA supports a
-v (verbose) command-line switch,
try to send mail to someone at a remote machine using that switch.
You should be able to observe the actual conversation between
your local sendmail and a remote machine's sendmail.
If you can, send mail addressed both to yourself on the local machine and to yourself on a remote machine. Compare and contrast the header part of each.
If you are at all fuzzy about the concept of envelope, review Section 1.7, "The Envelope" now. We will refer to envelopes often throughout this tutorial.
Leap ahead to Chapter 35 for additional information about specific headers.