184.108.40.206 PidTagReadReceiptRequested Property
Type: PtypBoolean ([MS-OXCDATA] section 2.11.1)
The PidTagReadReceiptRequested property ([MS-OXPROPS] section 2.872) specifies whether the e-mail sender requests a read receipt from all recipients (1) when this e-mail message is read or opened. If this property is absent, no read receipt is sent to the e-mail's sender. If the property is present, it is set to either 0x01, in which case the e-mail message's sender requests the read receipt from an e-mail client or server, or 0x00, in which case no read receipt is requested by the e-mail message's sender.
If an E-mail object that has its PidTagReadReceiptRequested property set to 0x01 is deleted, or it expires due to the time limit set by the PidTagExpiryTime property (section 220.127.116.11) before the read receipt for this e-mail is generated, a non-read receipt is generated and sent to the e-mail message's sender or designated receipt recipient (1).