Shared Email Templates
Attach files to Outlook emails with the Message attachments button
With the Message attachments button on the Shared Email Templates editor toolbar, you can automatically attach files from OneDrive, SharePoint, and URLs to Outlook emails.
When creating or editing your Outlook email template, select the
Message attachments button on the template editor toolbar.Choose where your file will come from (OneDrive, SharePoint, or a URL) and click the plus sign next to the corresponding option.
Select a file or enter a URL.
Close the Message attachments dialog.
A blue dot will appear on the Message attachments button:

Save the template.
When you use the message template, the specified attachments will be automatically added to your Outlook email.