Milter is the short name for Sendmail Content Management API. It also refers to software written using this API. Milter provides a plug-in interface for third-party software to validate, modify, or block messages as they pass through the MTA. Milters can process a message's connection (IP) information, envelope protocol elements, message headers, and/or message body contents, and modify a message's recipients, headers, and body. Possible uses for filters include spam rejection, virus filtering, and content control. In general, Milter seeks to address site-wide filtering concerns in a scalable way. Originally designed for sendmail, Milters written for sendmail can now be used with Messaging Server, although some limitations may apply (see below). For more information on Milter refer to the Internet.