Using Classic Outlook on Windows for personal email, calendar, and contact management
Hi alittle_glwa,
Good day.
Hope you are doing well. Thank you for posting in Microsoft Community.
According to your description, yes, I have gone through your situation, in order of your concern, seems like your concern environment is related to 3rd party apps that allow emails, I would like to share some information with you, as Microsoft has specific community channel resources where our related most valuable professional can provide possible information for certain different support scope and attributes So would you mind to connect and place your concern on our specific dedicated Microsoft Q&A forum community channel to get further possible information from our related community members?
Because, we are mainly focusing Office 365 exchange online related scenario on this forum community channel.
Here is URL link to place your concern: Microsoft Q&A forum channel
I am really appreciating your kind cooperation.
Stay safe and healthy.
Sincerely,
Darpan