Question : Domain users cannot send to mailman listserv

Users inside domain.local using email accounts with domain.org suffix cannot send mail successfully to externally hosted mailman list with address of [email protected].  I assume that Exchange simply does not know how to deal with the lists.domain.org suffix - but am not sure how to fix this.  External email accounts such as gmail are able to post to the list successfully.  Please let me know if you require more information.  Thank you.

Answer : Domain users cannot send to mailman listserv

The remote site could be looking at any number of things, including it may simply be configured in a way that presumes it is responsible for email for your domain and will not allow another server to send email for that domain to it. Many ISPs and server hosts will setup their network in that way.
The only way to know is to ask them what they are looking for, and whether there is an antispam restriction in place.

Simon.