Our organization requires from us to configure access to our internal exchange server in such a way that the roaming users should be able to connect to their mailboxes using MS Outlook; for this we have decided about 2 options;
2- RPC over HTTP
we have enabled IMAP services for the users to connect to their mailboxes using any form of internet connectivity. Now we have 3 domains
each domain is having a backend exchange server & 1 front end exchange server all running Win2k3 & exchange 2k3, only the front end server has a Public IP Address & this server is located inside a DMZ zone. After having done the configurations users can now connect to their mailboxes using a normal dialup, they can receive Internal & External emails, they send emails to internal users but the problem is they cannot send emails to external domains using their IMAP account settings, in the IMAP settings for incoming IMAP server & outgoing SMTP server i am using either the FQDN or the IP address of the Front End Server, i am guessing that this problem is somehow related to SMTP authentication because whenever i send an external email i receive a NDR saying that the exchange server cannot relay for the mentioned user.
Please explain in detail the steps that i need to take to enable this.