Can someone explain how email actually works?

[idea]

I'm asking this because I want to setup an IMAP server on my linux box. I compiled wu-imapd, but when I send mail to user@myhost, it does not get recieved. I'm very confused as to how this works, I think something is missing but I can't find a tutorial on this subject. Can someone explain exactly how email is sent and recieved for me, and if you can name some linux apps I'll need to configure to make this work? My ultimate goal is to be able to store my email on my linux (imapd) server, and read it from my winxp boxes on the home lan.

 

[Need4Speed]

you also need to configure sendmail or another MTA on your system. There are plenty of howto docs on how to setup an email server. linuxdocs.org might be a place to check.

Setting up sendmail is not a trivial task, for a beginner that is. Then again even some admin I know still have trouble with it. You may want to look into postfix. Ive been told its much simplier to setup.

 

[idea]

I just don't understand why I need sendmail to use imap. from what i know, sendmail is a util to, well, send email. but the email was all ready sent by someone, now it's en route to my imap server. where does sendmail come into this?

 

[kt]

I believe Sendmail (a MTA) is the agent used to transfer the message. Thus, the name MTA = message transfer agent. You'll need to configure Sendmail to deliver the message to your IMAP server.

 

[randal]

There are two parts to email -- the actual transiting of messages between servers and checking messages.

Part One - transiting email - Emails get transferred between what are called MTAs, or Message Transfer Agents. These MTAs speak to each other / pass messages using SMTP (simple mail transport protocol). Clients (like outlook/express) send messages to servers via SMTP as well, and then the server talks to other MTAs to get the mail to where it's supposed to be. When the destination MTA receives a message it has to do something with it. Usually it will end up in a spool directory, or write it to a users mail directory or however it does it -- somehow, that message gets stored on the server. The message is then ready for part two.

Part Two - Checking messages - Once the server has a copy of email, it has to make it available to the client (outlook or whatever). There are two popular ways to do this: POP and IMAP (post office protocol and internet message access protocol). When you check your mail, the POP or IMAP server reads what has been stored by the MTA (see part one) formats it for the POP3 or IMAP4 protocol and sends it on down to your client. POP works just like the post office, in that your mail is only in one place at a time, ever. It's either at the original writer's computer, on a server, or on your machine. Once you download a message to your PC via POP, it is gone off the server and the only copy of that message is on your computer. IMAP is server based -- every message you receive gets stored on the server, and the client only downloads headers; if you click on a message header, it then downloads the message and caches a copy locally. IMAP is great because all your messages are on the server, and hence accessible from anywhere. WIth POP3, once you download it onto your PC, it is only available on *THAT* PC, and not accessible from anywhere else.

So, to answer your question, you have the mail-checking part ready to go, but you need to setup an MTA to talk to other mail servers out there. Popular MTAs out there are Sendmail, Postfix, and Exim for Unix, and IMail, NTMail, and MailSite for windows.

cheers,
randal

 

[kevinthenerd]

Check your DNS. Perhaps the message isn't getting through because the MTA can't find the server. In the case of my university, email sent to user@saintleo.edu goes to the machine mail.saintleo.edu. The DNS needs to know those sort of things.

 

[idea]

I got it working, thanks.