KB-2052 System emails/process emails are no longer being sent with a "Connection refused" error

Symptoms

System emails for account creation are not sent.
System emails for resetting a password are not sent.
Process models with Send Email nodes are paused.
The application server log will contain one of the following errors:

ERROR com.appiancorp.ra.workpoller.WorkItemListener - The following exception occurred while attempting to complete work item [(WorkId: 14, WorkType: [AbstractMailRequest: from=null, to=<Email>, subject=<Subject>], Response: null, ServerName: NotificationsEmail)] - Exception:
javax.resource.spi.work.WorkCompletedException: com.appiancorp.process.engine.EmailBodyException: Email body failed to render
…
Caused by: javax.ejb.EJBException: com.appiancorp.process.engine.EmailBodyException: Email body failed to render
…
Caused by: javax.net.ConnectException: Connection Refused

ERROR com.appiancorp.process.workpoller.WorkItemListener - The following exception occurred while attempting to complete work item [[WorkId: 247, EngineId: notifications-email, Request: MailRequest:null as null by null, Response: null]] - Exception: 
javax.resource.spi.work.WorkCompletedException: java.lang.RuntimeException: Could not prepare email for: CompatibleEmailRecipients{locale=en_US, timeZone=IST, calendarId=gregorian, startPage=https://example-startpage.com/suite/tempo, emailAddresses=[a****.com]}
	at org.springframework.jca.work.SimpleTaskWorkManager$DelegatingWorkAdapter.run(SimpleTaskWorkManager.java:242)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
	at java.lang.Thread.run(Thread.java:748)
Caused by: java.lang.RuntimeException: Could not prepare email for: CompatibleEmailRecipients{locale=en_US, timeZone=IST, calendarId=gregorian, startPage=https://example-startpage.com/suite/tempo, emailAddresses=[a*****.com]}
...
Caused by: com.appiancorp.process.engine.EmailBodyException: Email body failed to render: MailBody{filename=/ntf/emailHtml/taskException_emailHtml.jsp}
...
Caused by: java.net.SocketException: Unexpected end of file from server

Cause

This issue occurs when the application server is unable to connect to the HTTP endpoint to render the email body. This can occur when there is a mis-configuration in custom.properties or if the HTTP listener has been removed from the application server configuration.

Action

Confirm that <APPIAN_HOME>/conf/custom.properties has the correct and expected configurations for MAIL_SERVER_AND_PORT and MAIL_SCHEME. See the documentation for more details.
Confirm that the standalone.xml (JBoss) and context.xml (Tomcat) configurations have declared the appropriate HTTP listener in order to accept HTTP connections.
Use a networking utility to confirm connectivity to the configured HTTP endpoint.

Affected Versions

This article applies to all versions of Appian.

Last Reviewed: July 2022