Symptoms

When a rule on a smartform attempts to send an email, the following error is received:
"An existing connection was forcibly closed by the remote host"

This feature was working until both the K2 blackpearl Setup Manager and the K2 Smartforms Setup Manager were run to change the database server. The only change made to the environment was the location of the database server.

Workflows continue to be able to send emails. This only affects the email action in smartforms. Dev and UAT environments are working fine using the same Exchange server.
 

Diagnoses

There are several different mechanisms used by K2 to send email. For example, client event notifications leverage MSMQ, whereas email events send directly using code, via either SMTP or EWS (depending on version and configuration).
K2 smartforms leverages the Mail Server environment field to send emails.
 

Resolution

Review and correct the "Mail Server" (default) Environment Library field for the environment in question. Remember there may be more than one environment defined, so you may need to verify which environment to check. Make sure the server specified is valid and available, and be sure there is no port number specified in the Environment field (e.g. ":25").