SharePoint Cannot Send Mail to Itself

When using the built-in mechanism to send email from SharePoint (or SPUtility.SendEmail), SharePoint stamps a X-Mailer header of: [crayon-515e8fb585e18-i/] If SharePoint is configured to send to the same SMTP service it is set to pick mail up from, SharePoint will drop any message with the above X-Mailer header indicating a possible message loop.