SMG Mail Routing for Microsoft Exchange

If your organization is using Microsoft Exchange for your email server infrastructure, below you will find details on routing your outbound email through the SecureMail Gateway server so that it can secure outgoing emails:

Setting up a "Send Connector" to the SecureMail Gateway

Login to your Exchange Admin center (EAC)
In the menu, Mail flow > Send connectors, and then click Add . This starts the New Send connector wizard.
On the first page, enter the following information:
- Name: Enter a descriptive name for the Send connector (for example, SecureMail Gateway).
- Type: Select Internet.
When you're finished, click Next.
On the next page, check "Route email through these smart hosts" click the "+" icon to add a route. Enter the ip address(es) of your SMG server(s) click "Save" then click Next.
On the next page, enter the following information:
- In the Address space section, click Add . In the Add domain dialog box that appears, in Fully Qualified Domain Name (FQDN), enter an asterisk (*), and then click Save. This value indicates that the Send connector applies to messages addressed to all external domains.
On the next page, in the Source server section, click Add . In the Select a Server dialog box that appears, select one or more Mailbox servers that you want to use to send mail to the internet. If you have multiple Mailbox servers in your environment, select the ones that can route mail to the internet. If you have only one Mailbox server, select that one. After you've selected at least one Mailbox server, click Add, click OK, and then click Finish.

For more information, please see the Microsoft article here: https://docs.microsoft.com/en-us/exchange/mail-flow/connectors/internet-mail-send-connectors?view=exchserver-2016

Note: you will also want to ensure the SMG is set to allow outbound email from all of your Exchange IP addresses by adding them via the SMG's admin console under "Network Config" -> "Host Access Control" in the "Allowed to Send Outbound" text box. This will allow your Exchange servers to relay outbound email through the SMG.