i have some external users complaining that they can't or are not receiving mail from our exchange server. i have set the external users up as a contact and have enabled the option to keep a copy and forward a copy to the external email account.
what is the best way to troubleshoot this as my gut feeling is that it might have something to do with greylisting and their isp, our outbound smtp server setting for the exchange server is with dyndns and i think maybe one of those servers might be on a blacklist and the external email client (user's) host/isp might just be dropping it.
the users are indicating that the email is actually available for view on their Outlook Web Access but it never gets to their external email account that is set to be the forwarded address. thanks.