Most of my customer use Exclaimer. Eversince Office 365 started rolling out, Excliamer started Cloud signature to support Office365 customers.
If you have used on-prem Exclaimer signature manager (Exchange Edition) in the past, you must have come across Policy Tester which used to be very handy in troubleshooting.
This policy tester was missing in the Exclaimer Cloud. This made troubleshooting really difficult,
But Exclaimer seem to have taken the feedback and brought this feature to the cloud as well. It is called “Signature Rules Tester”