same issue here, looks like the service is down on their side, since several days...
Proofpoint's rule service isn't down (new rules are being served properly it seems), but there might be an issue with their heartbeat stream. I'll send them an email and ask about it.
Complaining about a service (no matter if it's free or paid), without knowledge of the details, feels silly and not very constructive. For all you know Proofpoint might monitor crucial areas of the service actively and non vital parts less frequent, issues might occur only in specific scenarios, etc, etc.... just saying, context is important.
Not going to spend more time on this, but how would they send you an email if they don't know who you are... https://docs.opnsense.org/manual/etpro_telemetry.html If I read the error message correctly, the endpoint in your case isn't about actual statistics gathering (which you can easily validate by reading the also public source).Jumping to conclusions (about the quality of signatures) so easily is again not very constructive and considered harmful for those involved.Best regards,Ad
it's no problem at all to report it here, we can pass the message if needed.