The attFrom attribute is encoded as a TRP structure which encodes the display name and e-mail address of the sender, followed by the display name and address of the sender, followed by any necessary padding. The format for attFrom is as follows:
The sender-display-name is a null-terminated string that is padded with an additional null character, if necessary, to reach a 2-byte boundary. The padding at the end of the attFrom encoding consists of as many null characters as needed to reach a sizeof(TRP) boundary.
For the attFrom item, the TRP-structure is always a one-off encoding, so the trpid off the TRP-structure field is always trpidOneOff. The cbgrtrp, cch, and cb items correspond to the remaining fields of the TRP structure.
The cbgrtrp field is calculated as the sum of (sizeof(TRP) *2), the length of the null-terminated sender-display-name with its padding, and the length of the null-terminated sender-address.
The cch field is calculated as the length of the null-terminated display-name with its padding.
The cb field is calculated as the length of the null-terminated sender-address.
The sender-address is a string that is composed of four parts, the address-type, a literal colon (:), the address itself, and a terminating null character. For example, the string "fax:1-909-555-1234\0" would be a legal sender-address value.