Due to issues in our email service backend, the payment confirmation emails were not sent, to both the buyers and the merchants.
This happened between the time period Dec 06, 2018 23:00 IST to Dec 07, 2018 13:20 IST.
The emails are working now. We have switched to an alternate backend as an immediate measure to curb the problem. Meanwhile, the root cause of the original issue is under investigation.