~*~*POP3 Madness*~*~

Well . . .. I have never attempted to do a tutorial before . . . so this is probably going to suck. heh. This tut. Is on POP3. Here goes.

What is POP3 you ask? Well . . . it stands for Post Office Protocol Version 3. Something we all (well most of us) use every day. This is a simple method for retrieving and storing e-mail from remote mail servers. POP3 works in 3 stages. The Authorization Stage, the Transaction Stage, and the Update Stage.

Authorization Stage
Before you can access your mail you have to enter the proper identification to access the server. This is where you enter your user name and password unless you are using more secure means such as APOP, which required a timestamp and an ID. String. Next is the:

Transaction Stage
After your username and password are accepted your mail will automatically be downloaded to your system. While in the process of downloading these messages the server places an access lock on any new messages that are sent while the downloading process is still happening. These new messages will be stored on the server till you check your mail again. You can also mark messages for deletion in this stage but they will not be deleted till you reach the update stage.

Update Stage
During this stage any messages you marked for deletion will be removed. The access lock and the connection to the mail server will also be removed.

There are sets of POP3 commands for each stage mentioned above. For the Authentication stage you have the USER, PASS, and APOP commands. This is when you enter the username and password. The APOP command requests the encrypted timestamp and the identification string.

There are 7 commands for the Transaction stage. The STAT command will give information about the mail drop like the number of messages being received and the size of each. The LIST command will issue a line of information called a scan listing. If there are no arguments given the server will show information about the size of all the messages in your box. The message id is included in this list. Next we have the RETR command. The message id argument tells the mail server which messages to send. Once the messages are positively identified they are sent to the users system. The DELE command is how the messages are marked for deletion. Like I said earlier, these messages will not be deleted till the Update stage. Next is the NOOP command. I’m not sure exactly what this command is for. All I know is that you get a positive response back from the mail server. Next is the RSET command. Any messages that have been marked for deletion respond as unmarked by the mail server. After this happens the mail server resets the message number to its original value. Last is the TOP command. When the mail server issues a positive response the message headers, lines between the header and the body, and the body of the message are sent.

There is only 1 command for the Update stage. That would be the QUIT command. When this command is issued the server deletes those messages marked for deletion, removes the access lock, and drops the Tcp/ip connection to the mail server.

And that. . . . my fellow AOers is how POP3 works. Not that I have thoroughly confused you. . . . please add anything I may have left out.

Nice tut. How about simple troubleshooting tips?

Ran out of time, sorry.

*edit* sorry I have SMTP on the brain lately.

Quote:

Originally posted here by KorpDeath
Nice tut. How about simple troubleshooting tips?

telnet <ipaddress> 25
You should get a welcome message
type "helo" or if the daemon supports it "ehlo" , etc. etc.

Ran out of time, sorry.

I just want to point out for those reading this tutorial for information that port 25 is SMTP (Simple Mail Transfer Protocol) and that POP3 operates on port 110

Sorry bout that. Forgot to post the port numbers.

Here's a little addition to the tutorial in case anyone is curious as to what it looks like when some of these commands are issued. I have blocked out the server address and password for obvious reasons, but everything else still exists in it's natural state.

You can see there are two messages, then you view the contents of the first message. The first message is then deleted and a list is done again, confirming the existance of only one message.

Hope this helps those of you who are visual learners...

Very nice. Good job.

Nice job.

I think your tutorial is pretty good...

it sure says a lot more than i would have... but then again, thats why im ranked a newbie

Takes time. ;) Welcome to AO though.

dunno why you thought it would suck..

pretty darn good

Cheers

NOOP

NOOP is short for "No Operation." It does absolutely nothing. Useful for preventing timeouts if you want to stay connected to a server.

Ah. Ok. Thanks Vanguard. :)

I have to agree with Und3ertak3r this is d@mn good.... RogueSpy you should write more, I find this very helpful :).

Cya --d00dz--