A real-time email verification API is an excellent way of stopping disposable emails from getting into your database.
When a visitor keys in their address in your online form, an email verification API will check, in real-time, the quality of the address. In case the email address is found to be disposable, the API will prompt the user to correct the email address before they can proceed further.
That way, only valid, deliverable addresses will reach your database.
You can sign up to use real-time email verification API for free.
Additionally, you should consider using bulk email checker to clean your existing lists and remove fake and invalid addresses.