Apple Mail shows different amount of emails in inbox than server or outlook

I've found a post on the apple support community about this, but it had no solution. I have two inboxes in apple mail and outlook. One main inbox and one archive on a local NAS.
The amount between Apple Mail, Outlook and the web client from the email provider (that should show the absolute correct amount of emails) is different. Web client and Outlook is the same, Apple Mail always shows less emails. I'm not sure if there are actually some missing, because the numbers are so big, it would take ages to test that. Grouping of conversations is disabled, although it seems even if it's activated, it doesn't reduce the number of emails shown at the top of Apple Mail. Some examples: **Folder 1 Exchange (Main Inbox)**
Outlook and web client: 10.442 emails
Apple Mail: 8.962 emails
**Folder 2 Archive on NAS IMAP (with bigger difference):**
Outlook and web client: 112.769 emails
Apple Mail: 90.563 emails
I've removed and redownloaded both inboxes in Apple Mail multiple times.
It seems Apple Mail shows the correct amount. Is there any way to fix this and show the actual amount of emails?