A high level of spam complaints from your recipients is most likely the reason behind deliverability problems. If major mailbox providers (AOL, Gmail, Outlook, Yahoo) see recipients complaining about your emails, they will stop delivering them to subscribers' inboxes.
To help reduce these complaints, it is best practice to review your signup process and enable double opt-in on your ActiveCampaign forms. The double opt-in process allows subscribers to reconfirm their interest in receiving your emails, making them less likely to mark your email as spam.
Another way to help reduce complaints is to ensure that contacts understand what type of content they can expect to receive from you. You can include a description of the content on your sign-up form and include a permission reminder for each campaign you send.
If you make significant changes to your sending habits to improve your complaint rate, you will improve your reputation and deliverability. However, it will take at least 30-60 days before major mailbox providers re-evaluate your sender reputation.
Here are some of our best practice articles to help improve your deliverability and spam complaint rate: