Why Does "All Inboxes" Include iCloud Sent Mail

[Buadhai]

I'm trying to figure out what I did to cause iCloud Sent Mail to be included with All Inboxes. Sent Mail doesn't show up in All Inboxes with my iPad, iPhone or on my Mail account on my wife's M1 iMac. Only on my 2019 21.5" Intel iMac:

What did I do to cause this?

 

[usagora]

Check this thread out:

Sent mails showing in iCloud Mail Inbox, … - Apple Community

discussions.apple.com

Try disabling that setting:

 

[Buadhai]

How interesting. Thank you.