@Wolinski, James,Thanks for posting in Q&A.
From your description, I know that you want to deploy Mimecast for Outlook via Intune.
Based on my researching, there is no related feature in Intune. However, I find there are some other deployments you can refer.
1.Standalone Installation.
2.Group Policy Managed Deployment
3.Managed Deployment
4.Multi User Environment
Non-official, just for reference.
Hope above information can be helpful.
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