PostOffice is an excelent massmailer,
Auto add new emailaddreses,
Auto remove emailaddresses,
Auto delete bounced emailaddresses,
Auto check for new messages,
Handle mutiple mailinglists,
Auto replay when Subscribe,
Auto replay when Unsubscribe,
Send Plain or Html messages,
Send Attachement,
Excluded list,
Import mailinglists,
Auto check for dublicates,
Auto notify when new version is avalible,
Auto add Un/Subscribe info in email

Atomic Mail Sender is a feature-rich mass mailing and corporate broadcast software capable of sending of unlimited number of e-mail messages to unlimited number of recipients within very short period of time. The amazing speed is achieved by utilizing every existing bit of your Internet connection via multiple threads delivery technology. Messages are delivered using the built-in SMTP server that connects directly to recipients? mail service!