KB-1868 Appian fails to send email due to "4.3.1 insufficient system resources" error

Symptoms

Appian fails to send emails with the following error printed in the tomcat-stdOut.log file located in the <APPIAN_HOME>/logs directory: 

ERROR com.appiancorp.process.engine.UnattendedJavaActivityRequest - An error occurred while executing activity: id=536873858, classname=com.appiancorp.process.runtime.activities.SendEmailActivity
com.appiancorp.suiteapi.process.framework.ActivityExecutionException: Failed to send email
...
Caused by: com.sun.mail.smtp.SMTPSendFailedException: 452 4.3.1 Insufficient system resources

Cause

This issue occurs when the Exchange mail server is low on disk or memory and cannot process more requests.

Action

Engage the Exchange server team to investigate the resources used by the server and take the right actions for processing new emails. 

Affected Versions

This article applies to all versions of Appian using Microsoft Exchange as the mail server. 

Last Reviewed: February 2019