|
X-Sender: |
Some mail software expect 'Sender:' to be
an e-mail address which you can send mail to. However, some mail software
has as the best authenticated sender a POP or IMAP account, which you
might not be able to send to. Because of this, some mail software put
the POP or IMAP account into an X-sender header field instead of a Sender
header field, to indicate that you may not be able to send e-mail to this
address. |