On-Demand Mail Relay

366/UDP

On-Demand Mail Relay ( ODMR ) or Authenticated TURN ( ATRN ) is an extension for the e -mail protocol Simple Mail Transfer Protocol (SMTP). ODMR is defined in RFC 2645.

ODMR is an email service that allows users after proper authentication e- mail with an Internet Service Provider pick (ISP ) have dynamic IP addresses.

In contrast to the abzuholende POP3 e-mail, including the SMTP envelope is sent, which is important for the assignment to a receiver.

The client connects to the ODMR server and is authenticated by this. He asks all the emails from his domain. Then the client and server switch roles, the e -mails are transmitted over the existing TCP connection via SMTP.

This method is interesting for users who do not have a permanent Internet connection, for example, for a user with an ISDN dial access, and for users with changing IP addresses, which applies to many ADSL offerings, for example.

ODMR server

ODMR servers are already integrated in some MTAs ( such as ALT -N MDaemon ), but there are extensions for popular Unix MTAs such as Sendmail, Exim, Postfix and qmail.

ODMR client

As ODMR client can be used, for example, fetchmail. Example of a configuration in fetchmail:

Poll odmr.mailserver.de      proto ODMR:      user "username " password "password"      fetchdomains " domainname.de " When using Unix in this case is important that in / etc / services, the network ports are configured:

Commands

For example, for a typical connection ODMR:

> 220 EXAMPLE. NET on-demand mail relay server ready < EHLO example.org > 250 - EXAMPLE.NET > 250 -AUTH CRAM -MD5 EXTERNAL > 250 ATRN < AUTH CRAM -MD5 > 334 MTg5Ni42OTcxNzA5NTJASVNQLkNPTQo = < Zm9vYmFyLm5ldCBiOTEzYTYwMmM3ZWRhN2E0OTViNGU2ZTczMzRkMzg5MAo = > 235 now authenticated as example.org < ATRN example.org, example.com > 250 OK now reversing the connection < 220 example.org ready to receive email > EHLO EXAMPLE.NET <250 - example.org <250 SIZE > MAIL FROM: < 250 OK > RCPT TO: < 250 OK, recipient accepted ... > QUIT < 221 example.org closing connection literature

• RFC 2645 (ON -DEMAND MAIL RELAY ( ODMR ) SMTP with Dynamic IP Addresses )
• RFC 2554 (SMTP Service Extension for Authentication )
• RFC 2821 ( Simple Mail Transfer Protocol )