When sending an e-mail from outside of the company a bounce back message is sent. But the user will recieve the e-mail. When sending an e-mail from out side of the company to a distribution list where the user is on you get the same bounce back but the user doesn't recieve the e-mail.
I have checked that authentication is not required on the server from either her address or the distribution list.
this is the error message recieved on the bounce back.
Delivery has failed to these recipients or distribution lists:
Your message wasn't delivered because of security policies. Microsoft Exchange will not try to redeliver this message for you. Please provide the following diagnostic text to your system administrator.
Diagnostic information for administrators:
Generating server: cbcdom.local
#< #5.7.1 smtp;550 5.7.1 RESOLVER.RST.AuthRequired; authentication required> #SMTP#