I am trying to send a mail with html content, for the I tried to use the 'Send email alert' assertion. In that assertion I didn't see any options to select the content type.I tried the below things without success:-Just paste the html in the message body.-Create a variable using the type message and content type html and use that variable in the message body.
Unfortunately this is a current limitation of the assertion. This has been raised to our Engineering team as a feature request to be implemented in future versions of the gateway. You will be able to check future releases to see if it incorporates this fix.