Chapter Questions
Find out if your computing system allows you to invoke SMTP directly.
Build an SMTP client and use it to transfer a mail message.
See if you can send mail through a mail forwarder back to yourself.
Make a list of mail address formats that your site handles, and write a set of rules for parsing them.
Find out how a Linux system can be configured to act as a mail forwarder.
Find out how often your local mail system attempts delivery, and how long it will continue before giving up.
Some mail systems allow users to direct incoming mail to a program instead of storing it in a mailbox. Build a program that accepts your incoming mail, places your mail in a file, and then sends a reply to tell the sender you are on vacation.
Read the SMTP standard carefully. Then use TELNET to connect to the SMTP port on a remote machine and type the commands to ask the remote SMTP server to expand a mail alias. Verify that the server returns the correct expansion.
A user receives mail in which the To: field specifies the string important-people. The mail was sent from a computer on which the alias important-people includes no valid mailbox identifiers. Read the SMTP specification carefully to see how such a situation is possible.
POP3 separates message retrieval and deletion by allowing a user to retrieve and view a message without deleting it from the permanent mailbox. What are the advantages and disadvantages of such separation?
Read about POP3. How does the TOP command operate, and why is it useful?
Read about IMAP4. How does IMAP4 guarantee consistency when multiple concurrent clients access a given mailbox at the same time?
Read the MIME RFCs carefully. What servers can be specified in a MIME external reference?
If you use a smartphone with a limit on the number of data bytes received each month, would you prefer POP3 or IMAP4? Explain.
To disguise the recipients, spam messages often list Undisclosed Recipients in the To: field. Does your email interface allow you to send a message to a user that shows up in the user's mailbox as being sent to Undisclosed Recipients? Explain.