Sending e-mail with new comment failed - INVALID_CROSS_REFERENCE_KEY
Sending e-mail with new comment failed:
SendEmail failed. First exception on row 0; first error:
INVALID_CROSS_REFERENCE_KEY, invalid cross reference id: 
This error is indicative of a problem with the Organization-Wide Address. One of the following conditions probably exist:
Navigate to the E2CP Outbound Configuration and configure an available Organization-Wide Address.
This issue is due to misconfiguration.
See Salesforce Help & Training for more information about Organization-Wide Addresses.