I've found the issue I believe, the sending smtp server or maybe just an entry in the mailer script is not configured with a real/registered domain name. This causes an issue because receiving servers do reverse lookups on the domain to verify it's not a spammer, and it fails.
Here is the log entry on the receiving end:
SMTP-Activity-120513.log:05/13/12 21:44:59 SMTP-IN 0A8CD2959039430F85CEA042E7E66349.MAI 2756 50.57.144.177 EHLO EHLO flitetestweb.localdomain 250-server_name_redacted [50.57.144.177], this server offers 5 extensions 164 31
SMTP-Activity-120513.log:05/13/12 21:44:59 SMTP-IN 0A8CD2959039430F85CEA042E7E66349.MAI 2756 50.57.144.177 MAIL MAIL FROM:<apache@flitetestweb.localdomain> 501 Your domain does not seem to be valid. Could not find MX record for your domain. 86 45
SMTP-Debug-120513.log:05/13/12 21:44:59 ME-I0129: Sender apache@flitetestweb.localdomain prevented from sending email as domain invalid.
Who has access to the mail server (or maybe this is just a board reply to address?) to update the config to use a real domain name in the EHLO command?
All servers on the net that do basic spam reverse lookups on incoming email are rejecting mail from flitetest right now due to this.