Sometime on Apr 2, Nikhil Joshi assembled some asciibets to say:
X-Authentication-Warning: localhost.localdomain: nikhil owned process doing -bs
what does it mean?
It means that you changed the From address in your message. Your username on your machine is nikhil@localhost.localdomain, but you told your mail client (pine) to pretend that you are nikhiljoshi@subdimension.com
Of course, pine followed your orders. However, pine invoked mighty sendmail in -bs mode - that is SMTP via stdio mode. It did this running as you - nikhil.
Sendmail in its infinite wisdom noted that you - nikhil - who owned the humble pine process - were trying to send a mail as someone you weren't.
It checked to see how trustworthy you were, and found that you weren't. Therefore, it could not, in good concience, send the mail without first attaching an appropriate warning.
Hope this answers your question.
Philip