Configuring Microsoft365 with ExchangeDefender

If your Organization hasn't updated their SPF for Office 365:

Step 1: Configuration

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Your organization should have a SPF record for the domain(s) registered with Office 365. When implementing ExchangeDefender with Office 365, this record must be updated in the DNS zone for the relevant domain to include the following:

CONFIGURING OUTBOUND SMARTHOST CONNECTOR:

Step 2: Mail Flow

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Step 3: Add a connector

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Click the ‘+’ button and you’ll be greeted with the following context menu. Once you've selected 'Office 365' and 'Partner Organization' click the 'Next' button.

Step 4: New Connector

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ENTER the name of the connector (We suggest using ExchangeDefender).

CLICK check box for “Turn it On”. Click NEXT -

Select the option for 'Only when email messages are sent to these domains' and click the '+' button to add the domains

Step 5: Set the Connector Scope

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Put * in the domain name field and hit the 'Ok' button.

Step 6: Route Email

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SELECT 'Route email through these smart hosts' and then hit the '+' button.

Step 7: Add a Smart Host

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Add a smart host. Add 'outbound.exchangedefender.com' as you see it below.

Once you've entered the smart host hit the 'Save' button. From there you'll be taken to the TLS screen. Keep all options default as shown in the screenshot below.

Step 8: Validate Settings

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Validate your configuration by letting O365 send a test email. Enter in any email address of a recipient outside of your organization. Click the +  then click VALIDATE.

Microsoft365 and ExchangeDefender Connection Filtering

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Microsoft365 (Office 365) can at times, typically during high load or attack on the tenant, randomly block partner organizations from connecting to deliver email. In order to work around this issue, you need to follow the following steps.

Step 9: M365 Security Center

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Microsoft 365 security controls have been moved to Microsoft 365 Defender Security Center at https://security.microsoft.com

Upon login you should see a welcome screen with navigation on the left. The following click-through instructions will help you set everything up to securely receive email through ExchangeDefender without M365 interruptions.

Click on Policies & rules.

Step 10: Required Security Policies for M365 & ExchangeDefender

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Click on Threat Policies.

Click on Anti-Spam.

Click on Edit connection filter policy.

In the field "Always allow messages from the following IP addresses or address range add the following ranges:

65.99.255.0/24
206.125.40.0/24

Please note (#2) that once you type in the range you must click on the dropdown in the UI. It will convert the text you just typed in to a range and add an X next to it. If your browser / M365 is not doing what you see in this screenshot, please contact Microsoft support.

Finally, click on Turn on safe list and click on Save.

ExchangeDefender outbound network (outbound.exchangedefender.com) only relays email on behalf of our clients domains. Security and general Internet protocols prohibit us from sending email on behalf of other networks. As a security company it's our responsibility to prohibit spoofed or forged messages, for example someone using your organization to send emails as gmail.com or to launch an attack as a null sender.

Send legitimate M365 Out of Office (OOF) Responses

If you need to make sure Out of Office responses are sent out no matter what, here is the general process to follow at https://admin.exchange.microsoft.com

Step 1: Create new Exchange Connector

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This step will create a Microsoft M365 connector that will route all messages from your M365 tenant directly to the senders MX record (bypassing ExchangeDefender and assuring the OOF attempt is made)

Exchange > Mail flow > Connectors

+ Add a connector

+ Connection from: Office365

+ Connection to: Partner organization

+ Name:

+ What do you want to do after connector is saved? [CHECK] Turn it on

+ Use of connector: Only when I have a transport rule set up that redirects messages to this connector Next>

+ Routing: Use the MX record associated with the partner's domain

+ Security restrictions (accept defaults)

+ Validation Email / Review Connector Next/Save.

Step 2: Create a new Mail flow Rule

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This step will create a rule that forwards OOF messages to the Connector we made in step 1.

Exchange > Mail flow > Rules

+ Add a rule

+ Name: "Send Automatic Replies to connector Automatic Replies"

+ Apply this rule if: "The message properties"

+ The message type is Select one: "Automatic Reply"

+ Do the following: Redirect the message to: "the following connector"

+ Select "Automatic Replies (Out of Office) Only"

+ Click Next>

Accept defaults (Enforce)

Step 3: Publish new DMARC

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Make sure you configure DKIM signing to include Microsoft's signature, the instructions are here.

Next update the SPF record to include M365 connector, it should look like this: "v=spf1 include:proxy.exchangedefender.com include:spf.protection.outlook.com -all"

Step 4: Make sure everything works

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Validate your connectors, rules, SPF records, DKIM records, and confirm everything is enabled and enforced. One area our clients often overlook is enabling the Mail Flow > Rules: Confirm that the "Send Automatic Replies to connector Automatic Replies" - confirm that the rule is enabled.

Sending messages from external domains

To relay messages from external domains please see our ExchangeDefender IoT Connector feature.

ExchangeDefender protects you from SPAM and Phishing threats. To avoid M365 falsely identifying messages as fraud, follow these steps to add ExchangeDefender to tenant allow policies:

Manage Anti-Phishing Rules

1. Login to Microsoft 365 Defender Security Center at https://security.microsoft.com
2. Navigate to Email & Collaboration > Policies & Rules > Threat Policies

3. Under Microsoft Defender Policies we will be making changes to Anti-Phishing policies and Tenant Allow/Block Lists under Rules.

Policies & rules

Select Anti-Phishing under Policies. You will be presented with a list of policies, select "Office365 AntiPhish Default (Default)" or your default security policy. Expand Protection Settings. Confirm that "[ ] Enable spoof intelligence (Recommended)" setting is clear (unchecked) and click on Save.

Tenant Allow/Block Lists

Select Tenant Allow/Block Lists under Rules (Under Email & Collaboration > Policies & rules > Rules section of Microsoft Defender). Click on Spoofing and +Add 

Below is the content to paste into the domain pair list

Select Spoof type: External and Action: Allow. Paste the content below into the domain pairs text box and click on Add. Confirm that the new tenant Spoofing allow list matches the display below.

Disable M365 False Phishing Alerts

"Subject: Informational-severity alert: Phish delivered due to an IP allow policy"

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Go to security.microsoft.com and select Policies & Rules on the left. Select Alert Policy and make sure the following alert policies are deactivated (not blue) as in the screenshot below: "Phish delivered due to an ETR override" and "Phish delivered due to an IP allow policy"