Like any other email client, Gmail has a filter to decide whether an email is spam or not. Don't send emails to unengaged subscribers
Ask users to add you to their contact list How to pass through the Gmail spam filter? In this guide, you’re going to learn about precautions you can take to minimize the chances of being blocked by the Gmail spam filters.
Google in its security blog stated that their spam filter mechanisms prevent more than 10 million unsafe or unwanted emails from reaching the users. It uses machine learning and AI to decide whether to send an email to the spam folder or inbox.
Gmail has many spam filter barriers which are hard to pass by.
