Request Read Receipts in Mac OS X Mail
To make Mac OS X Mail request a read receipt for every message you send:
Open Terminal.
Type "defaults read com.apple.mail UserHeaders".
Press Enter.
If that command returns "The domain/default pair of (com.apple.mail, UserHeaders) does not exist":
Type
defaults write com.apple.mail UserHeaders '{"Disposition-Notification-To" = "Name <email@address>"; }'
replacing Name with your name and email@address with your email address.
The complete line could read "defaults write com.apple.mail UserHeaders '{"Disposition-Notification-To" = "Heinz Tschabitscher <sender@example.com>"; }'", for example.
If the "defaults read" command above returns a line of values that starts with "{" and ends in "}":
Highlight the entire line. It might read something like {Bcc = "bcc@example.com"; }, for example.
Press Command-C.
Type "defaults write com.apple.mail UserHeaders '" (excluding the outer quotation marks).
Press Command-V.
Type "'".
Insert '"Disposition-Notification-To" = "Name <email@address>"; ' in front of the closing "}" character, replacing Name with your name and email@address with your email address.
The line might now read
defaults write com.apple.mail UserHeaders '{Bcc = "bcc@example.com"; "Disposition-Notification-To" = "Heinz Tschabitscher <sender@example.com>"; }'
, for example.
Press Enter.