Forum Discussion
Exchange On-Prem Messages Delayed Delivery to Exchange Online
We have an on-premises Exchange server (2019) which relays messages from on-premises clients (scanners, servers, etc.) and most of our user mailboxes are in Exchange Online. Over the past few day...
Hijplace
- Is your Exchange 2019 server also your hybrid server that relays emails between on-prem and EXO, or do you send to EXO externally?
- Is it a single on-premises server being used?
- Do you use anonymous relay on your on-prem receive connector for the scanners and servers?
I would start with the following:
- Confirm that you have >10% free disk space on the C-drive to eliminate Exchange back pressure as an issue,
- Confirm that DNS is configured and working properly on your Exchange server, especially if you are using DNS round-robin for load-balancing,
- Assuming the 2019 Exchange server hosts the hybrid Send Connector, check other send connectors for possible conflicting config,
- Check that your hybrid servers' public IP is added to the Connection Filters in EXO,
- Check that your hybrid servers' public IP is not blacklisted.
I also believe it is recommended that your accepted domain should be set to Internal Relay in a hybrid scenario, although I don't think that will delay delivery.
Hope this helps.