Koozali.org: home of the SME Server
Legacy Forums => Experienced User Forum => Topic started by: gbaird on March 08, 2005, 04:14:20 PM
-
Maybe something to be ready for. I know some isp's are already have this port open. Don't when it is due to change however.
Email Ports
Email is sent around the Internet mainly from server to server using SMTP. Once delivered, clients may access it in a variety of ways, including POP3 and IMAP. This section DOES NOT cover Microsoft Exchange or other proprietary mail protocols.
The major upcoming change to email is the use of TCP port 587 "submission" for email, as defined in section 3.1 of RFC 2476 - Message Submission. This is planned to replace the traditional use of TCP port 25, SMTP.
3.1. Submission Identification
Port 587 is reserved for email message submission as specified in this document. Messages received on this port are defined to be submissions. The protocol used is ESMTP [SMTP-MTA, ESMTP], with additional restrictions as specified here.
While most email clients and servers can be configured to use port 587 instead of 25, there are cases where this is not possible or convenient. A site MAY choose to use port 25 for message submission, by designating some hosts to be MSAs and others to be MTAs.
This initiative is being promoted by, amongst others, the Anti-Spam Technical Alliance. See Anti-Spam Technical Alliance Technology and Policy Proposal, Version 1.0, 22 June 2004 (PDF)
We further recommend that SMTP authentication be implemented on the standard Mail Submission Port, port 587, and that ISPs encourage their customers to switch their mail client software (for example, MS Outlook, Eudora, and so on) to this port. Using this port will provide seamless connectivity that does not depend on if a network allows port 25 traffic.
In addition to SMTP, the other main email protocols are POP3 and IMAP, these are protocols for email clients to access their mailboxes. There are many other topics that are outside the scope of this page. For example, email addresses are described in RFC 2822 (obsoletes RFC 822), and SMTP authentication is covered in RFC 2554 - SMTP Service Extension for Authentication. Transport Layer Security (TLS) is covered in RFC 2246 - The TLS Protocol Version 1.0. SMTP over TLS is covered in RFC 3207 - SMTP Service Extension for Secure SMTP over Transport Layer Security.
The Network Sorcery RFC Sourcebook entry for SMTP also links to many relevant RFCs that cover the details of the protocol itself.
-
Maybe something to be ready for.
In the fullness of time, perhaps. Of only academic interest at the moment.