Configure Microsoft 365 with Secure Email

Introduction

This document describes the configuration steps to integrate Microsoft 365 with Cisco Secure Email for inbound and outbound email delivery.

Prerequisites

Requirements

Cisco recommends that you have knowledge of these topics:

• Cisco Secure Email Gateway or Cloud Gateway
• Command Line Interface (CLI) access to your Cisco Secure Email Cloud Gateway environment:
  Cisco Secure Email Cloud Gateway > Command Line Interface (CLI) Access
• Microsoft 365
• Simple Mail Transfer Protocol (SMTP)
• Domain Name Server or Domain Name System (DNS)

Components Used

This document is not restricted to specific software and hardware versions.

The information in this document was created from the devices in a specific lab environment. All of the devices used in this document started with a cleared (default) configuration. If your network is live, ensure that you understand the potential impact of any command.

Background Information

This document can be used for either on-premises Gateways or Cisco Cloud Gateways.

If you are a Cisco Secure Email administrator, your welcome letter includes your Cloud Gateway IP addresses and other pertinent information. In addition to the letter you see here, an encrypted email is sent to you that provides you with additional details on the number of Cloud Gateway (also known as ESA) and Cloud Email and Web Manager (also known as SMA) provisioned for your allocation. If you have not received or do not have a copy of the letter, contact  ces-activations@cisco.com with your contact information and domain name under service.

Each client has dedicated IPs. You can use the assigned IPs or hostnames in the Microsoft 365 configuration.

Note: It is highly recommended that you test before any planned production mail cutover because configurations take time to replicate in the Microsoft 365 Exchange console. At a minimum, allow one hour for all changes to take effect.

Note: The IP addresses in the screen capture are proportional to the number of Cloud Gateways provisioned to your allocation. For example,  xxx.yy.140.105  is the Data 1 interface IP address for Gateway 1, and  xxx.yy.150.1143  is the Data 1 interface IP address for Gateway 2. Data 2 interface IP address for Gateway 1 is  xxx.yy.143.186 , and Data 2 interface IP address for Gateway 2 is xxx.yy.32.98. If your welcome letter does not include information for Data 2 (Outgoing interface IPs), contact Cisco TAC to get the Data 2 interface added to your allocation.

Configure Microsoft 365 with Secure Email

Configure Incoming Email in Microsoft 365 from Cisco Secure Email

Bypass Spam Filtering Rule

1. Log in to the Microsoft 365 Admin Center
2. In the left-hand menu, expand Admin Centers.
3. Click Exchange.
4. From the left-hand menu, navigate to Mail flow > Rules.
5. Click [+] to create a new rule.
6. Choose Bypass spam filtering... from the drop-down list.
7. Enter a name for your new rule: Bypass spam filtering - inbound email from Cisco CES.
8. For *Apply this rule if..., choose The sender - IP address is in any of these ranges or exactly matches.
   1. For the specify IP address ranges pop-up, add the IP addresses provided in your Cisco Secure Email welcome letter.
   2. Click OK.
9. For *Do the following..., the new rule has been pre-selected: Set the spam confidence level (SCL) to... - Bypass spam filtering.
10. Click Save.

An example of how your rule looks:

Receiving Connector

1. Remain in the Exchange Admin Center.
2. From the left-hand menu, navigate to Mail flow > Connectors.
3. Click [+] to create a new connector.
4. In the Select your mail flow scenario pop-up window, choose:
   1. From: Partner organization
   2. To: Office365
5. Click Next.
6. Enter a name for your new connector: Inbound from Cisco CES.
7. Enter a description, if you wish.
8. Click Next.
9. Click Use the sender's IP address.
10. Click Next.
11. Click [+] and enter the IP addresses that are indicated in your Cisco Secure Email welcome letter.
12. Click Next.
13. Choose Reject email messages if they aren't sent over Transport Layer Security (TLS).
14. Click Next.
15. Click Save.
    
    

An example of how your connector configuration looks:

Configure Mail from Cisco Secure Email to Microsoft 365

Destination Controls

Impose a self-throttle to a delivery domain in your Destination Controls. Of course, you can remove the throttle later, but these are new IPs to Microsoft 365, and you do not want any throttling by Microsoft due to its unknown reputation.

1. Log in to your Gateway.
2. Navigate to Mail Policies > Destination Controls.
3. Click Add Destination.
4. Use:
   1. Destination: enter your domain name
   2. Concurrent Connections: 10
   3. Maximum Messages Per Connection: 20
   4. TLS Support: Preferred
5. Click Submit.
6. Click Commit Changes in the upper right-hand of the User Interface (UI) to save your configuration changes.

An example of how your Destination Control Table looks:

Recipient Access Table

Next, set the Recipient Access Table (RAT) to accept mail for your domains:

1. Navigate to Mail Policies > Recipient Access Table (RAT).

   Note: Make sure the Listener is for Incoming Listener, IncomingMail, or MailFlow, based on the actual name of your Listener for your primary mail flow.

2. Click Add Recipient.
3. Add your domains in the Recipient Address field.
4. Choose the default action of Accept.
5. Click Submit.
6. Click Commit Changes in the upper right-hand of the UI to save your configuration changes.

An example of how your RAT entry looks:

SMTP Routes

Set the SMTP route to deliver mail from Cisco Secure Email to your Microsoft 365 domain:

1. Navigate to Network > SMTP Routes.
2. Click Add Route...
3. Receiving Domain: enter your domain name.
4. Destination Hosts: add your original Microsoft 365 MX record.
5. Click Submit.
6. Click Commit Changes in the upper right-hand of the UI to save your configuration changes.

An example of how your SMTP Route Settings looks:

DNS (MX Record) Configuration

You are ready to cut over the domain through a Mail Exchange (MX) record change. Work with your DNS administrator to resolve your MX records to the IP addresses for your Cisco Secure Email Cloud instance, as provided in your Cisco Secure Email welcome letter.

Verify the change to the MX record from your Microsoft 365 console as well:

1. Log in to the Microsoft 365 Admin console.
2. Navigate to Home > Settings > Domains.
3. Choose your default domain name.
4. ClickCheck Health.

This provides the current MX Records of how Microsoft 365 looks up your DNS and MX records associated with your domain:

Note: In this example, the DNS is hosted and managed by Amazon Web Services (AWS). As an administrator, expect to see a warning if your DNS is hosted anywhere outside of the Microsoft 365 account. You can ignore warnings like: "We didn't detect that you added new records to your_domain_here.com. Make sure the records you created at your host match those shown here..."  The step-by-step instructions reset the MX records to what was initially configured to redirect to your Microsoft 365 account. This removes the Cisco Secure Email Gateway from the incoming traffic flow.

Test Inbound Email

Test inbound mail to your Microsoft 365 email address. Then, check to see that it arrives in your Microsoft 365 email inbox.

Validate the mail logs in Message Tracking on your Cisco Secure Email and Web Manager (also known as SMA) provided with your instance.

To see mail logs on your SMA:

1. Log in to your SMA.
2. Click Tracking.
3. Enter the needed search criteria and click Search;and expect to see such results:

To see mail logs in Microsoft 365:

1. Log in to the Microsoft 365 Admin Center.
2. Expand Admin Centers.
3. Click Exchange.
4. Navigate to Mail flow > Message trace.
5. Microsoft provides Default criteria to search with. For example, choose Messages received by my primary domain in the last day to start your search query.
6. Enter the needed search criteria for recipients and click Search and expect to see results similar to:

Configure Outgoing Email from Microsoft 365 to Cisco Secure Email

Configure RELAYLIST on Cisco Secure Email Gateway

Refer to your Cisco Secure Email welcome letter. In addition, a secondary interface is specified for outbound messages via your Gateway.

1. Log in to your Gateway.
2. Navigate to Mail Policies > HAT Overview.



   Note: Make sure the Listener is for Outgoing Listener, OutgoingMail, or MailFlow-Ext, based on the actual name of your Listener for your external/outbound mail flow.

3. Click Add Sender Group...
4. Configure the Sender Group as:
   1. Name: RELAY_O365
   2. Comment:  <<enter a comment if you wish to notate your sender group>>
   3. Policy: RELAYED
   4. Click Submit and Add Senders.
   5. Sender: .protection.outlook.com
      

      Note: The . (dot) at the beginning of the sender domain name is required.

   6. Click Submit.
   7. Click Commit Changes in the upper right-hand of the UI to save your configuration changes.

An example of how your Sender Group Settings looks:

Enable TLS

1. Click <<Back to HAT Overview.
2. Click the Mail Flow Policy named: RELAYED.
3. Scroll down and look in the Security Features section for Encryption and Authentication.
4. For TLS, choose: Preferred.
5. Click Submit.
6. Click Commit Changes in the upper right-hand of the UI to save your configuration changes.

An example of how your Mail Flow Policy configuration looks:

Configure Mail from Microsoft 365 to CES

1. Log in to the Microsoft 365 Admin Center.
2. Expand Admin Centers.
3. Click Exchange.
4. Navigate to Mail flow > Connectors.
5. Click [+] to create a new connector.
6. In the Select your mail flow scenario pop-up window, choose:
   1. From: Office365
   2. To:Partner organization
7. Click Next.
8. Enter a name for your new connector: Outbound to Cisco CES.
9. Enter a description, if you wish.
10. Click Next.
11. For When do you want to use this connector?:
    1. Choose: Only when I have a transport rule set up that redirects messages to this connector.
    2. Click Next. 
12. Click Route email through these smart hosts.
13. Click [+] and enter the outbound IP addresses or hostnames provided in your CES welcome letter.
14. Click Save.
15. Click Next.
16. For How should Office 365 connect to your partner organization's email server?
    1. Choose: Always use TLS to secure the connection (recommended).
    2. ChooseAny digital certificate, including self-signed certificates.
    3. Click Next.
17. You are presented with the confirmation screen.
18. Click Next.
19. Use [+] to enter a valid email address and click OK.
20. Click Validate and allow the validation to run.
21. Once complete, click Close.
22. ClickSave.

An example of how your Outbound Connector looks:

Create a Mail Flow Rule

1. Log in to your Exchange admin center.
2. Click mail flow;be sure to be on the rules tab.
3. Click [+] to add a new rule.
4. Choose Create a new rule.
5. Enter a name for your new rule: Outbound to Cisco CES.
6. For *Apply this rule if..., choose: The sender is located...
   1. For the select sender location pop-up, choose: Inside the organization.
   2. Click OK.
7. Click More options...
8. Click add condition button and insert a second condition:
   1. Choose The recipient...
   2. Choose: Is external/internal.
   3. For the select sender location pop-up, choose: Outside the organization .
   4. Click OK.
9. For *Do the following..., choose: Redirect the message to...
   1. Select: the following connector.
   2. And select your Outbound to Cisco CES connector.
   3. Click OK.
10. Return to "*Do the following..." and insert a second action:
    1. Choose: Modify the message properties...
    2. Choose: set the message header
    3. Set the message header: X-OUTBOUND-AUTH.
    4. Click OK.
    5. Set the value: mysecretkey.
    6. Click OK.
11. Click Save.

Note: To prevent unauthorized messages from Microsoft, a secret x-header can be stamped when messages leave your Microsoft 365 domain; this header is evaluated and removed before delivery to the Internet.

An example of how your Microsoft 365 Routing configuration looks:

Finally, access the CLI for your Cisco Secure Email Gateway.

Note: Cisco Secure Email Cloud Gateway > Command Line Interface (CLI) Access.

Create a message filter to inspect the presence and value of the x-header and remove the header if it exists. If no header exists, drop the message.

1. Log in to your Gateway via the CLI.
2. Run the Filters command.
3. If your Gateway is clustered, hit return to edit the filters in Cluster mode.
4. Use the New command to create a Message Filter, copy, and paste:
   
   

   office365_outbound: if sendergroup == "RELAYLIST" {
   if header("X-OUTBOUND-AUTH") == "^mysecretkey$" {
   strip-header("X-OUTBOUND-AUTH");
   } else {
   drop();
   }
   }

5. Hit return one time to create a new, blank line.
6. Enter [.] on the new line to end your new message filter.
7. Click return one time to exit the Filters menu.
8. Run the Commit command to save the changes to your configuration.

Note: Avoid special characters for the secret key. The ^ and $ shown in the message filter are regex characters and use as provided in the example.

Note: Please review the name of how your RELAYLIST is configured. It can be configured with an alternative name, or you can have a specific name based on your relay policy or mail provider.

Test Outbound Email

Test outbound mail from your Microsoft 365 email address to an external domain recipient. You can review Message Tracking from your Cisco Secure Email and Web Manager to ensure it is appropriately routed outbound.

Note: Review your TLS configuration (System Administration > SSL configuration) on the Gateway and the ciphers used for Outbound SMTP.  Cisco Best Practices recommends:

HIGH:MEDIUM:@STRENGTH:!aNULL:!eNULL:!LOW:!DES:!MD5:!EXP:!PSK:!DSS:!RC2:!RC4:!SEED:!ECDSA:!ADH:!IDEA:!3DES:!SSLv2:!SSLv3:!TLSv1:-aNULL:-EXPORT:-IDEA

An example of Tracking with successful delivery:

Click More Details to see the complete message details:

An example of Message Tracking where the x-header does not match:

Related Information 

Cisco Secure Email Gateway Documentation

• Release Notes
• User Guide
• CLI Reference Guide
• API Programming Guides for Cisco Secure Email Gateway
• Open Source Used in Cisco Secure Email Gateway
• Cisco Content Security Virtual Appliance Installation Guide (includes vESA)

Secure Email Cloud Gateway Documentation

• Release Notes
• User Guide

Cisco Secure Email and Web Manager Documentation

• Release Notes and Compatibility Matrix
• User Guide
• API Programming Guides for Cisco Secure Email and Web Manager
• Cisco Content Security Virtual Appliance Installation Guide (includes vSMA)

Cisco Secure Product Documentation

• Cisco Secure Portfolio Naming Architecture