Does PayPal IPN require SSL certificate?

I'm using a plugin called PayPal IPN for wordpress. The plugin generates an IPN URL, however, when I try and enter this IPN in to PayPal I get the following error message:

"We're sorry. That URL won't work. Please enter an “https” URL."

This was the plugin generated URL:

http://ift.tt/1WI4BT8

I have entered other URLs before and have never seen this message, although the IPNs weren't sent properly. Does this mean that I have to get an SSL certificate for IPNs to be sent through? Thank you.

via Chebli Mohamed