Hi @Alexander Kaa ,
By "Business Gmail accounts", are you referring to the Google Workspace (formerly called Gsuite) account?
If this is the case, sorry that I don't have a Google workspace account to help check it from my side, but based on my research, seems to me that Google workspace account is not yet fully supported in the New Outlook preview.
Although in this blog it's officially announced that New Outlook preview is starting to support third-party accounts, but it only mentions about Gmail, Yahoo and iCloud which are all seemingly to be personal accounts.
Also found the following article which indicates that the account supportability in New Outlook preview is expand to 3rd-party "Personal accounts":
Windows 11’s new Outlook app now supports Gmail, personal accounts
(Please Note: Since the web site is not hosted by Microsoft, the link may change without notice. Microsoft does not guarantee the accuracy of this information.)
Given this, I'd suggest trying to share your feedback about this from inside the new Outlook preview app: Select Help and choose Feedback. Hopefully this can be fully supported in the further update.
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