Computing 205/406 & IT8

Tutorial #5

1. What is your preferred electronic mail address at Bendigo? In general, what is the format of an Internet email address?

2. What is the general format of an RFC822 electronic mail message?

3. The DATA operation in the SMTP protocol uses a "." on a line by itself to indicate the end of the mail message. What do you think happens if this occurs in the message?

4. The SMTP protocol, like the FTP protocol, uses a 3-digit code in all communications from the server. From the example given in the lecture, can you generalise about the significance of the first digit of this code? What about the second digit?

5. What is MIME? Explain briefly how MIME works to send a file (eg, a GIF image) as an email message. What is a MIME Multitpart message?

6. What is the Post Office Protocol (POP) used for?

7. In the SMTP protocol, the sender uses the "Rcpt to:" operation to specify the mail destination. What do you think happens if this is different to the "To:" address in the message itself?

Practicals Exercise

• When you receive mail on the departmental systems, it is stored in your system mailbox. This is a file in "mailbox format". Examine your system mailbox and explain what "mailbox format" looks like. In particular, how do you tell where one message ends and the next begins?

• The "mail spooling" system on a Unix host can be examined using the mailq command. Try it.

• OK, time for some experimental computer science. In the last question, above, the problem of conflicting addresses was given. Try it yourself (be sure to use a sensible From: address in the header so that the mail system can reply to you), and see how the mail system on the recipient computer handles it. Be aware that every electronic mail transaction is logged on all systems, so you would be well advised to stick to local hosts, and addresses of people you know.