Message Transfer Envelopes and Attached Messages

A message transfer envelope (MTE) contains the outgoing message to be delivered as an attached object. This message object can be opened with the MAPI IMessage interface. This is the only attachment the MTE can have until the gateway calls the MAPI SetReadFlag function to indicate that it has accepted responsibility for the message. After the gateway accepts the message, it can add more attachments to the MTE if necessary.

Note  For an MTE with a single attached message, the attachment number of the message is always zero. For a message with a single attachment, the number of the attachment is always zero.

Delivery reports and nondelivery reports carry the original message as an attachment if the MAPI property PR_CONTENT_RETURN_REQUESTED was set to TRUE on the original message. For more information about delivery report and nondelivery report structures, see Reports.