cc:Mail channels are used to convert messages to and from the RFC 822 and MIME message formats used by PMDF to the formats used by the cc:Mail Import/Export utility. The cc:Mail channel programs combined with the Import/Export utility plus some mechanism to transfer files between systems will produce an effective gateway between PMDF and cc:Mail.

The cc:Mail channel programs attempt to convert as much of MIME as possible to formats cc:Mail can understand. However, limitations in cc:Mail make a complete conversion impossible, so in some cases the conversion will be limited in scope. In particular, the limits imposed by cc:Mail on the number of parts (e.g., attachments) in a multipart message make it necessary to consolidate multipart messages in some cases. cc:Mail is also incapable of handling nested multipart structures, so any sense of nested structure is lost in the conversion.