Delivering queued mails on Demand
		
Overview :

When a mail cannot be sent, the mail is queued for future delivery. In most of the mail server, the server periodically dispatches all of its mails. After an attempt, the mails will be put back to the queue and will be dispatched after the queue timeout period. That is, there is a delay in attempting the next delivery attempt.

This could call for an mechanism by which the neighbour SMTP servers can invite or inform the mail server that it has come online and ready to receive/relay mails.

Solution :

When a SMTP server comes up, it could send an INVITE command to its neighbour SMTP servers inviting that they can dispatch mails addressed to this SMTP server. 

250-INVITE

If neighbour SMTP server does not recognize the INVITE command, it would return 5xx return code. The sending SMTP server can ignore the reply.

The SMTP servers that can understand and allow INVITE command, can start dispatching mails addressed to the SMTP server, issued INVITE.

Issues/Security Considerations :

This draft would discuss about identifying neighbour SMTP servers, could be through the site's MX records.

This might introduce denial of service or some related issues. The draft would analyze all the issues and solutions.


27-Oct-2003						Madan Ganesh V
							Hewlett-Packard
							madan-ganesh(_dot_)v(_at_)hp(_dot_)com