We don't store passwords for any of your emails accounts. Then, you might be wondering how your email is retrieved. When you first setup your email account and you login to your email through Polymail, your email creates an authentication key specific for your Polymail app. That authentication key (an encrypted token) is what allows you and you alone to retrieve email. The authentication key isn't transferrable and you can revoke access via your email or via Polymail at anytime. 

Important note for IMAP accounts:

If you are connecting to an IMAP account, because the IMAP protocol does not have support for OpenAuthentication (e.g. Gmail, Outlook, etc.), your passwords will be encrypted and stored.