check sent messages

[Mark Van Crombrugge]

Last night a mail was sent to a group of recipients but it seems like  
only a few persons received the message.
 The command mailq says "Mail queue is empty, the mail logfile  
doesn't show any errors.

How can I check if a certain message was sent sent?
Is there a way to log every outbound message's From and To fields?
Thanks in advance!
Mark