1.8 Things to Try

• 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 intact?

• In the file sendstuff, we created a one-line header that began with 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 the Preface.)

• 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.