I tried activation with a second email address, it does not work.
Yes, I think that Jay is right. There is something going on over at eM Client. You could write to them and ask. The sales department mentioned in the error can be contacted by email at firstname.lastname@example.org.
Registered a second Free license and tried using it but still I’m seeing the same error.
I have sent an email to eM Client. Hopefully they will respond.
if your error message says “This computer cannot be activated due to a violation of our license policy. Please contact our sales department.” it means you were banned for breaking our license policy, this is most commonly using a Free license for commercial/work/business use.
Contact our sales department if you believe there was a misunderstanding or if you have more questions - email@example.com.