[BUG] Can't add 3rd party email clients inboxes to Windows 10 Mail App

Hello there!
Have anyone noticed a bug in 1903 Windows 10 Insider Build 18334 (19H1) which you cannot add 3rd party email inboxes to Windows 10 Mail & Calender Metro App (like you cannot add Yahoo! Mail or Gmail to see your inboxes)?

For instance, look at my attachment where you can find Live mail inbox; however there is no other inbox for Gmail although it is already added on the right panel!

Please tell me if anybody have the same issue or it is only my PC.

Thanks!

Regards,
addas

What version of Mail are you on? Check in Mail, Settings, About. Mine is Version 16005.11231.20142.0 and I have both Outlook and Gmail folders.