Connecting to SMTP Hosts with Internet Mail Service

You can set up a Microsoft Exchange Server with Internet Mail Service on the bastion host that routes mail between your organization and the SMTP hosts on the Internet. To minimize risk, you can make this a dedicated Internet mail server that does not contain user mailboxes. If an intruder does gain access to the bastion host, none of the data stored in users mailboxes or public folders is at risk because only messages in transit are stored at the bastion host.

If you are using a packet filter, you must configure it to allow TCP connections to and from port 25 on the Microsoft Exchange Server computer.