ISP reputation is based on
- volume history,
- spam complaints,
- spam trap hits,
- bounce percentages,
- proper authentication and
- blacklist entries.
To build and maintain a good reputation
- require double opt-in,
- scrub your lists for bounces,
- do not buy, rent or borrow third-party lists,
- setup a postmaster and abuse email address for any complaints,
- monitor feedback loops,
- authenticate with DKIM/DomainKeys,
- authenticate with SenderID,
- authenticate with SPF, and
- do not mail to old or invalid database contacts.
Lead Liaison automatically appends an unsubscribe link to the bottom of email messages to provide recipients with the choice of opting out instead of hitting the spam button.