KB-XXXX Setup tab error in Send Email node, "The system has encountered a problem"

Symptoms

 The Setup tab of a Send E-mail Smart Service node throws the following error:

The system has encountered a problem. 
We're sorry! A problem occurred while processing your last request. 
Please contact the system administrator for more information.

Additionally, the application server logs the following error:

INFO [ajp-nio-8009-exec-2300] org.apache.catalina.core.StandardWrapperValve.invoke 2018-10-23 02:27:10,836 [ajp-nio-8009-exec-2300] 
ERROR com.appiancorp.common.struts.BaseAction - Error executing action: com.appiancorp.ix.binding.UnresolvedRuntimeException: type=content, sourceId=SYSTEM_DOC_EMAIL_HEADER: 
java.lang.NullPointerException [{1}] cannot be found. [{1}] cannot be found.

Cause

emailHeader.html or emailFooter.html are missing.

Action

Workaround

Affected Versions

This article applies to all versions of Appian.

Last Reviewed: October 2018