On 2020-10-01 08:19, [email protected] wrote: > Hello, > > I am managing a Postfix mail relay service in our internal network. The > relay itself is more permissive than the downstream SMTP server. So it > is possible, and indeed it regularly happens, that my relay accepts a > message which is subsequently bounced by the downstream server. There is > no way to inform the original sender what happened to the message after > the relay accepted it. > > Is it possible to delay closing the SMTP connection from the original > sender until the response from the downstream server is received, and > then respond accordingly in the original connection? > > I could imagine this would imply some complications in terms of > performance, and the question what happens if downstream is not > available. But in the way it would appear the advantage of telling the > original sender what happened to a message, outweighs the disadvantages.
This seems to be a job for a reverse proxy, such as NGINX (which already supports SMTP). NGINX is event-driven, so it can handle thousands of connections without a significant performance hit. > Regards, > > Lucas Sincerely, Demi
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