Hello all,
We running O365 in a Hybrid environment. We have been migrating users in small batches from our on-prem Exchange 2010 environment. With this setup emails come in to our Exchange 2010 servers first and those emails going to users on the cloud will flow to the Hybrid server 2013 and up to O365. We have had an instance where messages began to fill up on the CAS queues for the SMTP Relay to the hybrid server. We restarted the Hybrid and that resolved the backup and all was well again. We made sure updates were installed and all was good. Then the issue happened again yesterday. It began to backup and a restart resolved it. Has anyone seen this issue? Any thoughts on resolution? Thanks for the help.