Dear Officegoogl,

Thanks for choosing Microsoft Community.

Based on your description, I know your consult. Since Office 365 Business Premium is now Microsoft 365 Business Standard, and the Business Standard plan includes everything in Business Basic, plus:

• Desktop versions of Office apps with premium features
• Easily host webinars
• Attendee registration and reporting tools
• Manage customer appointments

Therefore, if you want to use desktop office apps, you may upgrade to Microsoft 365 Business standard plan. For the detailed information about Microsoft 365 Business Basic and Microsoft 365 Business Standard plan, please see: Reimagine productivity with Microsoft 365 and Microsoft Teams.

By the way, here is an article for your reference: Upgrade to a different plan.

Moreover, for your problem when receiving outside documents, as far as I know, Outlook Web App blocks attachments that have the certain file name extensions by default. And as the administrator, you can change the Outlook Web App mailbox policy to include and exclude the file types that you want. Here is the detailed instructions: Office 365 users can't open or view attachments in Outlook Web App.

Hope this can help. If there is any update, please feel free to let me know. Your understanding and co-operation are highly appreciated.

Thanks for your precious time. Have a nice day.

Sincerely

Katherine