Microsoft Exchange Online allow you to create a max of 300 Transport Rules. If for any reason, you have exceed the 300 Transport Rule limit, you will get the below error message when you create the 301 Transport Rule.
If you approach Microsoft, even if you are an enterprise organization, they will say no to increase the Transport Rule limit. Microsoft will ask you to consolidate the Transport rules and later they may consider your request.
So, how to consolidate?
- Delete the Transport Rules, which are not in enabled status.
- Do a cleanup by removing the unwanted Transport Rules by validating whether the transport rules are really in use by viewing the Rule Hits.
(Get-MailDetailTransportRuleReport -TransportRule “Rule Name” -StartDate (Get-Date).AddDays(-7) -EndDate (Get-Date)).count
If the count shows as 0 for the above command, you can consider that rule is not in use and can deleted the Rules.
- Validate the rules and see if any rules can be combined to reduce the Transport Rule number.
Still the numbers are not reducing then show the consolidation details Microsoft Support and they may consider your request.