This is a long-standing problem that I attempt to tackle now and then hoping that new eyes might see something that I have missed. Over the years I have tried every rational solution that I've seen. Nothing works.
Time to throw in the towel and just put up with it.
Kind of like the self-assigned IP addresses on my iPad and iPhone and the fact that no Mac web browser can display certain Apple Support pages.
Unfortunately, many things don't work the way they're supposed to.
This post lasted for about 2 years with no updates since 2019.. It seemed to be the best source of information when trying to google this issue - something I too have done many times over the past few years.. This time I took it a bit more seriously.
I ended up in an email conversation with an iCloud Mail Team email address at Apple. Initially they started responding to me like I was a user and as a user I needed to move the mail to the inbox. I explained that I've tried everything but this problem continues to occur even with Mail.app junk mail filtering turned off and even if I move emails to the inbox (emails at some later date still end up back in junk when I would not have expected them to)
Either I got on to a different person responding or that person finally understood what I was getting at and they responded with:
iCloud Mail uses reputation systems, user feedback, and other dynamic filtering technology to route or reject inbound messages to our users. Do note that false positives may occur from time to time. In such cases, moving the message in the Junk folder to the inbox will ensure that future messages from the sender would be delivered to the inbox. The action will also help train our server-side reputation systems.
The email that ended up in my junk was a Google Calendar invite - the first Google Calendar invite from a particular user sent to me (note: the email address I use is a @me.com address, not @mac.com or @icloud.com)
I dug further and found a previous Google Calendar invite from another person for the first time and the headers pointed to that also ending up in my junk mail.
First Google Calendar email from [email protected] to [email protected]
Code:
X-Apple-MoveToFolder: Junk
X-Apple-Action: CLXJUNK/Junk
X-ICL-SCORE: 4.3330340300
X-ICL-INFO: <some encoded string I couldn't figure out>
x-spam-flag: yes
x-suspected-spam: true
Second Google Calendar email from [email protected] to [email protected]
Code:
X-ICLOUD-MAIL-BWL: 1
X-Apple-MoveToFolder: INBOX
X-Apple-Action: WL/INBOX
X-ICL-SCORE: 3.3330333300
X-ICL-INFO: <some encoded string I couldn't figure out>
So it looks like Apple have some system that marks emails as junk and from the current tone of the email thread I'm having there isn't really a way to fix it other than moving emails to your inbox to assist future emails from that person (or from that system (Google Calendar)? or both?) to end up in your inbox.
I suspect the "X-ICLOUD-MAIL-BWL" flag maybe means "this has been whitelisted in the past"? if a user has moved previous emails to their inbox? I dunno to be honest.
I'm still in conversation with Apple and hopefully I can learn more.. when googling these headers NOTHING useful came up - hopefully someone in the future googling this can land on this page.