How can I resolve the error “Could not connect to SMTP server due to one of the following reasons: No SMTP service running on "mailserver.domain.com", TLS or SSL required by server, authentication required, or unknown domain in user.name@domain.com"

You may encounter the above following error message “Could not connect to SMTP server due to one of the following reasons: No SMTP service running on "mailserver.domain.com", TLS or SSL required by server, authentication required, or unknown domain in user.name@domain.com“ when going to “SilkCentral Test Manager | Administration | System | Notification | Email” and entering valid connection details. If you inspect the Application Server log file you will also see the error:
 
SendFailedException: Sending failed; nested exception is: class javax.mail.MessagingException: Could not connect to SMTP host: mailserver.domain.com, port: 25; nested exception is: java.net.ConnectException: Connection refused: connect

The above issue has been known to be caused by virus scan software which blocks the connection of third party applications which try to communicate with the email server. To resolve the error it is recommend if possible that you add an exception for the SilkCentral Application Server to the Virus Scan software this can be done manually or by speaking to your IT department for further assistance.