Table 1: Command-line parameters.
| Parameter | Meaning | Direction | Medium |
| $InEnv | Envelope of current message. | In | File |
| $InMsg | Envelope and body of current message. | In | File |
| $InBdy | Body of current message. | In | File |
| $InXmlBdy | Formatted body of current message. | In | File |
| $InAttachDir | Current message's attachments. | In | Directory |
| $Status | Status text returned from the external system but does not contain message data. | Out | File |
| $OutEnv | New message envelope. | Out | File |
| $OutBdy | New message body. | Out | File |
| $OutXmlBdy | New formatted message body. | Out | File |
| $OutMsg | New message envelope and body. | Out | File |
| $OutAttachDir | New attachments. | Out | Directory |
| $Temp | Temporary file created by the MHS which the external system can use any way it likes. | None | File |
