Currently, SharePoint Online and OneDrive for Business send external sharing invitations via the Microsoft Online Services Team address (which is generic and difficult to identify which site is from).
Starting today the external sharing invitation emails will now be coming via the Exchange Web Services. Sharing invitations will now come from the sharing users mailbox or a SharePoint owned “No Reply” address.
The main reason for the above change was to resolve the confusion and helping users find email based on SharePoint team site name or an individual’s name from OneDrive For Business.
You can find more information on how to manage external sharing for your SharePoint Online environment.