How to delay delivery of emails based on recent soft bounce activity with Exim

Question

I am running Exim 4.74, I am sending solicited bulk email.

AOL at times soft bounces us saying we have been temporarily rate-limited and should try again in some number of minutes. We would like to honor there requests and stop to send AOL emails for a short period of time before resuming.

Here is the ideal way our exim server would operate: 1. Emails are delivered outbound as usual. 2. We receive a soft bounce (4xx) to one of our delivery attempts 3. Emails destined to the host of the received soft bounce are sent to the queue for 15 minutes 4. 15 minutes have elapsed, exim resumes immediately sending emails to the temporarily delayed host, queue runners begin to deliver emails to the temporarily delayed host.

Does anyone have any experience implimenting this sort of exim configuration?

Thank you!

Answer 1

The default configuration file should already be configured to retry in 15 minutes. This will solve part of your problems and is generally sufficient to handle rate limiting and other conditions which result in temporary deferral of deliveries.

I am not aware of any mechanism which allows you to capture the deferrals and dynamically add the domain to a block list.

Check the mechanisms available in the specification for retry rules. Perhaps addingg the domain which is rate limiting you to queue_smtp_domains would help somewhat. You may want to combine that with a domain specific retry rule.

You may want to check your configuration to see why you are getting rate limited. DNS errors, or SMTP server configuration errors may contribute to your server being rate limited.