The Subscription Manager add-in (SUM) is designed for automatic adding/deleting subscribers to/from Microsoft Outlook 2000/XP/2003 mailing lists based on special e-mail messages from them (requests). A request is a standard e-mail message that contains a command for SUM in its ''Subject'' field. Subscription Manager is the first mailing list management software for Microsoft Outlook.

SUM is capable of processing ''subscribe'', ''unsubscribe'' and ''help'' requests. When subscribe or unsubscribe request is received, the user is added to or deleted from the distribution list specified in the request. Upon receipt of a help request, a message with information about current subscription status and request sending rules is sent to the user. The adding to the distribution list can be made both with obtaining confirmation from the user and without it.

Once a request is processed, SUM sends auto-reply with information about processing result. Auto-replies are created based on Outlook templates using special macros (expressions that are automatically replaced when sending a message). You can make any desired changes to appearance of SUM auto-replies by changing the auto-reply templates.

Since 1.1 version, Subscription Manager also support mailing lists with subscription confirmation to exclude subscriptions from fake and another''s emails. And now Subscription Manager support almost features of standalone products for mailing list management.