Half of 11 years messages have disappeared...

Hello to the Microsoft community,

   and first thanks a lot for reading this !

I write you from Paris, close to Pere Lachaise, I have lived here fore 28 years, in a little apartment (19 m2), I teach half time in poor suburbs but I do also short movies (fiction) and photography (portraits). I love epistolary correspondence, so I enjoy using Microsoft Outlook...

  One week ago I have lost half of my correspondence ! I am very sad and I hope someone is going to help me for finding a solution.

  First, I say with what I work:

Macbook Pro (2018), OS Catalina 10.15.7, Outlook for Mac 16.66.1

  And I tell what's happened...

  In Riga where I was for thinking about a new movie, there was connexion problems. At a moment I had the colored wheel which means the application has a problem. It was the first time I saw this with Outlook. I have waited for but as I was not at home, I decided to force to quit and come back.

  And all messages had disappeared ! This basis is with all my messages since 2013.

   I am not too afraid because I know I work with imap.orange.fr and I know my messages are also there. So I connect Outlook and the messages are coming back slowly. I feel it could be a source of mistakes but I decide to trust. And 5 or 6 hours later, Microsoft Outlook shows me my last messages. I think I am saved !

    It was Thursday. But today, Sunday, I had some e-mails with heavy attachments so I decided to check with Orange.fr the size of all my messages because Orange doesn't store more than 10 Go. I know I was around 9,96 Go... Everytime there is saturation I throw away old attachments.

   And I see: 5,3 Go !!!

   It means I have lost quite half...

   How can I do to find half missing?

   Of course I have a backup hard drive but how mix the 5 Go which are now in the basis, with the 10 Go in the backup drive ? I wouldn't want a 15 Go basis with many repetitions...

   All the best from Paris,

         Patrick