If you would like for Marketo MSI to be supported for Office 365, you can raise it as an idea in our community: https://nation.marketo.com/community/product_and_support/ideas
Our product managers refer to these ideas for improving on existing features and implementing new features in future releases.
The supported list of outlook plugins can be found in the following document:
https://experienceleague.adobe.com/docs/marketo/using/product-docs/marketo-sales-insight/msi-outlook...