RoboPostman for Mac

From Koingo Software:

Create a personal look and feel to every message you send out, without the extra effort! RoboPostman allows you to custom tailor messages to include dynamic content specific to each recipient. Include birthdays, custom notes, links with rotating affiliate codes, and more. Use the "Visual" editor to create brilliant messages with fonts, colors, links, and images without needing to know HTML.

Manage address lists with an unlimited number of records and specify as many custom fields as desired. Include anniversaries, nicknames, phone numbers, or even security questions. Easily import and export these lists for future use in other messages, or use the powerful built-in Text, CSV or Address Book import features to retrieve data from other sources.

List scrubbing is a vital feature of RoboPostman that will help keep your mailing list clean. Have it automatically connect to a POP3 mail account and check for unsubscribe requests or bounce noitifcations. It will automatically scan your list, set the status of recipients to the applicable state (bounced or unsubsribed), and then delete the message from the mail server. If your campaign is huge and POP3 access is too slow for your purposes, have RoboPostman open a text file and scrub all e-mail addresses it finds.

RoboPostman is mail server friendly. Supporting Secure Socket Layer (SSL) and TLS encryption, it also boasts numerous fall-back techniques in the event servers return errors during a mail operation. Other useful features are the ability to specify a range of recipients in an address list to mail, and the ability to limit how many messages are sent per mail server connection.