I would also like to know the answer. We are experiencing many blocks due to timeouts and too many connection issues and wondering if we are already being throttled?
421 tmo-ibgw-5002a.ext.cloudfilter.net cmsmtp 149.72.130.204 blocked AUP#CNCT
452 4.1.0 <bounces+14645690-9958-+17072081891=tmomail.net@prod.ehi.com> server temporarily unavailable AUP#MXRT
421 tmo-ibgw-5003a.ext.cloudfilter.net cmsmtp too many sessions from 149.72.130.204 AUP#CNCT
The gateway is still operational, as I have had the need to use it recently. Some messages get through, while others don’t. It seems to be dependent on where the message is originating.
AUP is Acceptable Use Policy. From the information @esherman posted above, it looks like Cloudfilter is blocking the messages. The too many sessions error is self-explanatory. Most servers, if not all, have a limit on the number of connections from any particular server.