I’m on an open source email list, where a lot of users self host their email. They have all the correct things done by the book. But gmail sends them all to my spam box, despite my continuing to mark them as not spam. Some even don’t appear in the spam box, despite other users on the list receiving the emails just fine.
If this email list does not rewrite "from" header, and modifies the email contents, that's the issue. Unfortunately, many still do. Such setup just won't work in the modern email world anymore.
