In such environments, you can use a Hub Transport server to send/receive internet mail.
Default Receive Connectors
The default installation of a Hub Transport server creates two Receive Connectors:
1) Default Receive Connector: listens on SMTP port 25
2) Client receive connector: intended for remote clients to submit mail - this listens on port 587.
The Default Receive Connector only accepts mails from authenticated senders/hosts. It is configured to accept mail from Mailbox Servers, other Hub Transport servers, and Edge Transport servers.
To allow it accept inbound internet mail in an environment without an Edge Transport server, you need to configure it to accept mail from anonymous senders. Here's how you can do this from the Exchange shell:
set-ReceiveConnector -identity "Name of Default Connector" -PermissionGroups AnonymousUsersTest the configuration by telnetting to the SMTP port of the server and sending a message.
- Make sure one or more Accepted Domains exist for domain(s) you've registered with a domain registrar
- Create an Email Address Policy (or modify an existing one) to generate email addresses for your recipients using the domain(s)
- Firewall: Most commercial firewalls require 2 configuration changes. 1) A rule that maps the internal IP address of the server to an external IP address reachable from the Internet. 2) An "access" rule that allows inbound SMTP traffic (tcp port 25) to the server
- DNS: 1) Ensure the DNS zone(s) for these domains can be reached from the internet. Many domain registrars now provide free DNS hosting with a domain registration, and allow you to make changes using a web browser. 2)Create an A record: Create an A record that resolves to the external/NATted IP address 3) Create an MX record that points to the A record.
- By default, Hub Transport servers do not have anti-spam agents installed. Read related post "HOW TO: Install anti-spam agents on Hub Transport server".