I tried the following:
var x = mailItem.Sender;
var y = mailItem.SenderEmailAddress;
var z = mailItem.SenderName;
All three variables have the value null. This the mailItem being edited in the ispector and I can access all other iformation like receptients, etc.... Any clue as to how get the sender name?
This one is even better and works anywhear:
MailItem.SendUsingAccount.SmtpAddress;