Hi @Glenn Maxwell ,
There are two ways you could try:
1.You could hide the retention policy UI in outlook 2016:
https://support.microsoft.com/en-au/topic/hide-the-retention-policy-ui-in-outlook-2016-62afe117-f230-ad99-254c-b1ae15f56f90#:~:text=%20Hide%20the%20retention%20policy%20UI%20in%20Outlook,8.1%2C%20move%20your%20mouse%20to%20the...%20More%20
2.When you create a new retention policy, there is a “-MustDisplayCommentEnabled" parameter. It is turned on by default and you can choose to turn it off.
You could refer to the documentation:
https://learn.microsoft.com/en-us/powershell/module/exchange/new-retentionpolicytag?view=exchange-ps
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