Emails Send To Spam/Promotions

Nothing is really set in stone when it comes to email deliverability. Each case is a little bit different, and the fact that Google (primarily) doesn't share their flagging procedures makes it harder to get back on track once your messages start landing anywhere besides the actual inbox.

The best thing you can do, especially if it is a newer domain, is to briefly put your automated sequences on hold until you "warm-up" the domain itself a little bit. This is usually done by sending emails to known valid email addresses, making sure that you mark them as not spam / not phishing / or in this case as "not promotions" once they are received, and if possible, replying to the email address that was placed in the promotions folder originally.