For SPAM related diagnostics, study of email headers is
almost necessary.This note provides information on how to
view email headers under various email clients (including public
websites). Many of us may not regularly use or even have
seen some of those email clients, but our users might be
using the same and our support team have to help them
to locate those headers.

Site Name-> http://community.mxtoolbox.com/blog/2009/05/18/how-to-get-email-headers-a-guide-from-mxtoolbox/