For G Suite.
How to avoid notification emails from G Suite being misclassified as “spam” e-mail?
Please contact your agency for the reason for misclassification as “spam” e-mail as logic for classification of spam e-mail is not disclosed by G Suite.
FYR when our some customer reported the similar problem in the past it was solved following the settings described in the URL below.
■ Settings for bypassing spam e-mail
* Please register the Google notification e-mail address as non-spam e-mail in the spam e-mail settings.