Is there a way to let the contains of a subject line to pass through the spam filter? I know you are whitelist domains and emails. I am trying to let emails pass through that all will have the same subject line. Thank you all for any advice.
The short answer is yes, through an Exchange Online transport rule that detects subject content and then sets the SCL to '-1'. However I can't stress enough that this would be a very poor solution as someone could easily use the subject line to bypass spam filtering for your tenant.