All relaying has stopped working suddenly this morning. We run a Exchange 2013 Hybrid server within an office 365 config. We have a relay connector under Receive connectors for Exchange in prem 2013 server. I noticed when relaying stopped our Que viewer started to build up to 7k messages. All normal internal and external email is flowing fine but anything that relays hits the hybrid server and is stuck in QUE., I have restarted the hybrid server and restart the MS Transport service as well.
Any other ideas?