If the URL in notifications are sent with http protocol instead of https even though the application is secured. Then try the below solution.
1. Stop the application
2. Go to <Drive>:\ManageEngine\ServiceDeskPlus-MSP\Conf
3. Keep a backup of the file called "TrayIconInfo.xml"
4. Now edit the file and search for the Keyword "http".
5. You will find the below entries :
<SDP-PROPERTIES RequestScheme="http" WebPort="8080"/>
<!--SDP-PROPERTIES RequestScheme="https" WebPort="80" ipToBind="192.168.112.177"/-->
6. Just add an extra "s" after http highlighted above and save the same.
7. Start the application.
This should solve the issue related with notifications missing https in the URL's