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Support Article

Inbound Emails delayed due to loop in processing



The email listener gets stuck in a loop-back condition responding to auto replies and Delivery Status Notifications, DSNs

Error Messages

javax.mail.MessagingException: A3 NO Server Unavailable. 15;
nested exception is:
com.sun.mail.iap.CommandFailedException: A3 NO Server Unavailable. 15
Caused by: com.sun.mail.iap.CommandFailedException: A3 NO Server Unavailable. 15
at com.sun.mail.iap.Protocol.handleResult(
... 7 more

Steps to Reproduce

Not Applicable

Root Cause

A defect in Pegasystems’ code or rules:

There is a case when processing Delivery Status Notifications, DSNs, it is possible to get into a loop when responding to the status notification, if and only if, the respondent continues to send email to the listener and does not respond only one time to a specific sender.

As an example you might see the following if Debug is set on the email listener class logger. (
DEBUG EMAIL.B17326Listener.Listener|from([email protected]|sub([Auto-Repl) [email protected] - Setting response header 'subject' to 'Re: [Auto-Reply] Re: [Auto-Reply] Re: [Auto-Reply] Re: [Auto-Reply] Re:' It is seen that the subject indicates a repeated attempt to re-send the reply to the origin, who in turn resends the reply to the email listener inbox.
In most cases it seems that the auto reply, or mailer daemon will respond once per sender and the problem is averted.


Perform the following local-change:

The following Dynamic System Setting will prevent the problem when there is a known string in the subject line from the respondent.

Ruleset: Pega-IntegrationEngine
Purpose: Email/AutoReplySubject
(Capital letters may be a comma separated list)

Related details
  • Process Delivery Status Notifications (DSNs) - Specify whether the listener is to process email messages that are Delivery Status Notification (DSN) messages. See PDN article How to create an email service that responds to AutoReply and Delivery Status Notification messages. When cleared, the listener does not invoke the email service for messages with DSNs

Suggest Edit

Published March 26, 2017 - Updated October 8, 2020

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