E-mail and Anti-Spam - Understanding Headers

Below are depictions of email headers so that you review the SenderBase Reputation scores (SRBS).

In the header, lines 1-4 are different for Gmail customers and Exchange customers. The images below demonstrate that difference.

First four lines of the header for a Gmail customer:

Gmail header, first four lines

First four lines of the header for an Exchange customer:

Exchange header, first four lines