MimeMessageSender Property

public MailboxAddress Sender { get; set; }

Property Value

Implements

The "Sender" field specifies the mailbox of the agent responsible for the actual transmission of the message. For example, if a secretary were to send a message for another person, the mailbox of the secretary would appear in the "Sender" field and the mailbox of the actual author would appear in the "From" field. If the originator of the message can be indicated by a single mailbox and the author and transmitter are identical, the "Sender" field SHOULD NOT be used. Otherwise, both fields SHOULD appear.

Reference