Email login principles
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Posted By:   ppp_rex
Posted On:   Friday, July 5, 2002 07:39 AM

Does anyone know (who understands this in details) how login to email on the distant network works? (example: login into yahoo email from one of AOL hosts and sending message to hotmail.com)? What I know is the following: between one of AOL hosts and one of yahoo email servers the TCP connection must be establish. First, TCP connection from AOL host to yahoo web server will be established (destination port 80), and then email client software will be used for actual login. Then another TCP connection will be established between email client and email server (generally both on two different machines) over the yahoo intranet. Which destination port is used I have no ANY idea (any RFC describing this?). When email is typed in and just    More>>

Does anyone know (who understands this in details) how login to email on the distant network works? (example: login into yahoo email from one of AOL hosts and sending message to hotmail.com)?
What I know is the following: between one of AOL hosts and one of yahoo email servers the TCP connection must be establish.

First, TCP connection from AOL host to yahoo web server will be established (destination port 80), and then email client software will be used for actual login. Then another TCP connection will be established between email client and email server (generally both on two different machines) over the yahoo intranet. Which destination port is used I have no ANY idea (any RFC describing this?).

When email is typed in and just about to be sent smtp aplication on yahoo email server runs smtp protocol from sender (yahoo) to receiver on hotmail email server (via TCP connection - destination port 25; SMTP is formulated by Postel in RFC 821).

Could anybody add more to this or correct my confusing thoughts?

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Re: Email login principles

Posted By:   Jorgen_Nordqvist  
Posted On:   Sunday, July 7, 2002 08:04 PM

Email exchange _always_ takes place on port 25, regardless of how you actually interact with the mail server. Port 80 is only used between your web browser and a web-based email client, not for the actual transfer of emails between servers. Hence, if you use MS Outlook, outgoing emails will be sent using SMTP on port 25.

This is all documented in RFC821 and RFC822.

Jorgen

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