Connect Application - Creating an Outbound Email Flow

Customers currently using the Connect Application are advised to complete their onboarding setup as soon as possible, as the Connect Application is scheduled to be discontinued on the 31st of January, 2024.

This article provides information on configuring outbound email flow using Mimecast Connect Application, including steps for Microsoft 365, on-premise/hybrid, and hosted Exchange environments, ensuring secure and efficient email routing.

If you are not using the Connect Application, see the Connect Process Guides page.

Introduction

To send emails from your mail server through the Mimecast gateway, you are required to create an SMTP send connector with our smart hosts. Your smart hosts are displayed in the Connect Application. Using a single connector with two smart host ensures there is round-robin traffic and provides contingency in the unlikely event of a fail-over.

The process of creating an outbound mail flow connector differs according to the Exchange version you are using:

• Microsoft 365.
• On Premise / Hybrid / Hosted Exchange.
• Hosted Exchange.

Your Microsoft 365 tenant domain must be added to the list of internal domains available in the Mimecast Administration Console. See Managing Internal Domain & Subdomains.

Microsoft 365

You can create an outbound email flow connector in Microsoft 365, by using the following steps:

1. Log in to the Microsoft 365 Administration Console.
2. Select Admin | Exchange.
3. Select Mail Flow | Connectors.
4. Create a Connector.
5. Complete the New Connector - Select Your Mail Flow Scenario dialog as follows:

Field / Option	Description
From	Select "Microsoft 365" from the drop down list.
To	Select "Partner Organization" from the drop down list.

6. Click the Next button.
7. Complete the New Connector - New Connector dialog as follows:

Field / Option	Description
Name	Enter a name for the Connector.
Description	Optionally, enter a description for the Connector.
Turn It On	Select this option to enable the Connector.

8. Click the Next button.
9. Select the Only When Email Messages are Sent to These Domains option.
10. Click the + Icon to add the recipient domains that should use this connector.

4. Enter a value of * to route all outbound emails through Mimecast.
5. Click the OK button.
6. Click the Next button.
7. Select the Route Email Through These Smart Hosts option.
8. Click the + Icon to add the smart hosts from the table below for the region where your Mimecast service is hosted:

Region	Microsoft 365 Account Hostnames
Europe (excluding Germany)	eu-smtp-o365-outbound-1.mimecast.com eu-smtp-o365-outbound-2.mimecast.com
Germany	de-smtp-o365-outbound-1.mimecast.com de-smtp-o365-outbound-2.mimecast.com
United States of America	us-smtp-o365-outbound-1.mimecast.com us-smtp-o365-outbound-2.mimecast.com
United States of America (B Grid)	usb-smtp-o365-outbound-1.mimecast.com usb-smtp-o365-outbound-2.mimecast.com
Canada	ca-smtp-o365-outbound-1.mimecast.com ca-smtp-o365-outbound-2.mimecast.com
South Africa	za-smtp-o365-outbound-1.mimecast.co.za za-smtp-o365-outbound-2.mimecast.co.za
Australia	au-smtp-o365-outbound-1.mimecast.com au-smtp-o365-outbound-2.mimecast.com
Offshore	je-smtp-o365-outbound-1.mimecast- offshore.com je-smtp-o365-outbound-2.mimecast- offshore.com

6. Click Save.
7. Click Next.
8. Select the following options:

• • Always use Transport Layer Security (TLS) to Secure the Connection (recommended)
  • Issued by a trusted certificate authority (CA)

6. Click Next to verify your settings.
7. Click Next.
8. Add an Email Address of a recipient from a domain external to your organization.
9. Click Validate.
10. Once Microsoft 365 has successfully validated your settings, click Save.

On Premise / Hybrid

For more information on how to create an outbound mail flow connector, view the relevant article below:

• SMTP Connector - Exchange 2019 / 2016 / 2013
• Lotus Domino - Setting up an SMTP Connector

If you utilize non-static public IP addresses, refer to Configure SMTP Authentication on Exchange.

Hosted Exchange

To set up your outbound email, forward our outbound routing instructions to your HEX provider to make the required changes. Ensure they consider the following when setting up your outbound email:

• In a multi-tenanted HEX environment, there are normally a number of customers on one server sending email outbound via a single Microsoft Exchange send connector. If one of the customers on the HEX platform implements Mimecast, their outbound email must be separated from the rest of the clients on that HEX platform.
• All outbound email should then be sent to Mimecast for delivery, as opposed to being sent to the internet using the standard Microsoft Exchange send connector. This is called Sender Address Based Routing, which is not a standard Exchange function.
• To implement Sender Address Based Routing, either a third party tool or additional hardware is required to send outbound email directly to Mimecast.