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Email Allow List and Best Practices

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If you use Microsoft 365 Defender to protect your email, follow these steps to prevent it from blocking legitimate, simulated phishing attacks used for training from Barracuda.

Security Awareness Training Cloud Migration

The Barracuda Security Awareness Platform will be migrating to a new cloud provider. In order to ensure there aren't any disruptions with your testing and/or training campaigns, please allow the IP address block on your email security system or service.

Allow List for Campaign Emails

When you run a Security Awareness Training email campaign, emails are sent to your domain. These emails might be classified as suspicious by email security systems. To ensure that Security Awareness Training campaign emails reach their intended recipients, you may need to add Security Awareness Training campaign email domains to the Allow lists in your email security systems. 

Important! If you are using Barracuda Email Gateway Defense, or are otherwise setting up Microsoft 365, you are instructed to create a mail flow rule that bypasses the additional spam filtering that Microsoft 365 performs. As long as that rule is in place, these SAT campaign emails will flow directly to the users' inbox and the Allow List instructions here do not apply. See also Using Microsoft 365 Defender with Security Awareness Training, which covers important steps that can help prevent false positives.

If you are not setting up with Microsoft 365 or using Barracuda Email Gateway Defense, meet with your email security system vendor or administrator to have them allow the Security Awareness Training campaign email domains or the IP addresses for the Security Awareness Training mail servers. If you decide to allow by domain, include the email server domain you select when you configure the domain.

Emails coming from standard Security Awareness Training servers to your organization will originate from one or more of the IP addresses in this address range. Allow these IP addresses for the Security Awareness Training email servers on your email security system or service:


All SMTP servers sending emails for Barracuda-supplied domains identify themselves in the Received header as Barracuda recommends that you check only the domain if you are allow listing by the Received header. The domain should only be in the two oldest Received headers. Here is an example of Received headers:

Received: from (3.145.232.yy) by (NNN.NNN.NNN.NNN) …; Wed, 3 Feb 2022 11:15:05 +0000

Note: yy above could be any number from 16 to 23.

Received: from localhost (localhost []) by (Postfix) with ESMTP id NNNNNNNNNN for <>; Wed, 3 Feb 2022 05:15:05 -0600 (CST) (NNN.NNN.NNN.NNN) is the host name and IP address of the receiving mail server. NNNNNNNNN is a numeric ESMTP id.

The message Return-Path header will be set to reply_xxxxxxxxxx@[from domain], where xxxxxxxxx is replaced with a random identifier and the From domain will be replaced with one of the domains specified in the campaign’s email accounts. Note that some mail gateways and mail servers might strip the Return-Path header before it reaches the user’s mailbox. If you plan to use the Return-Path header, you must confirm that the header is not stripped before it reaches the user’s mailbox. 

The Envelope Sender Address is not the same as the From header and will not match. The Envelope Sender Address matches the Return-Path. The From header matches one of the Email Accounts specified in the campaign.

Changes in the Google and Outlook mail clients that now expose that the Return-Path is set to [mailbox] required an update to the way return mail is routed. The Envelope Sender Address and the Return-Path header are now set to an email address with the same domain as specified in the Security Awareness Training email account.

  • If you are using the Envelope Sender Address or the Return-Path header to allow email messages from the Barracuda system, you must allow based on the campaign’s email account From email address or From email domain.
  • If you are using an email-only domain that you own, the Return-Path will still be set to

The SMTP domains are configured with both the Sender ID Framework (SPF) and the DomainKeys Identified Mail (DKIM) DNS TXT record types. The Barracuda inbound SMTP servers identified by DNS MX records are used for receiving replies, delivery notifications, and out-of-office messages from your email system to Barracuda.

  • 10 (,

Please update any mail host references to use IPs. To be safe they should include the entire bock of IP addresses: (

Note: You can also configure the system to use third-party SMTP email servers for some campaigns. This is a non-standard option that requires additional allow list details.

Preventing Emails from Going to Junk Email

Microsoft 365

To prevent emails from going to the junk email in Microsoft 365:

  1. In Microsoft 365, open the Exchange Online Admin Center. Navigate to Protection > Spam Filter.
  2. Create a new spam filter. Name it something like Allow <campaign_name> domain email.
  3. In the Allow Lists area, locate the Allowed Sender area. Enter the From email address(es) that you use in each of your campaigns (e.g.,
  4. In the Applied to area, add your domain information.
  5. Save this filter and make it a higher priority than the default spam filter provided with Microsoft 365.

Note that you must perform these steps again for future campaigns that use different emails and domains.

Office 2013

There are two ways to prevent emails from going to the junk email in Office 2013.

Method 1: Safe Sender

Create a Safe Sender list and deploy it using Group Policy. Refer to the Microsoft documentation on safe senders for details. 

Method 2: Completely Disable the Junk Email Folder

Use a Group Policy to set the following registry settings to completely disable the Junk email folder in each user's Outlook client:

  • HKEY_CURRENT_USER\Software\Policies\Microsoft\office\14.0\outlook
  • DWORD: Disable Antispam
  • Value of 1 disables the junk filter

The Outlook Email client determines which content goes into the Junk email folder, and it is not controlled by Exchange.

Note that the Group Policy setting does not apply if your users use web mail to check their email. Refer to the next section, Disabling the Junk Email Folder in Microsoft 365, for more information.

Disabling the Junk Email Folder in Microsoft 365

You can disable the Junk email folder for all mailboxes by using PowerShell.

This technique is provided as an alternative method for handling junk and spam emails. Your organization must determine if it is appropriate to remove Junk folders for all inboxes.

To disable the Junk email folder:

  1. Connect to your Microsoft 365 instance with PowerShell.
  2. Run this command to get the current setting for all users:
    Get-Mailbox | get-mailboxjunkemailconfiguration
    When you initially run this script, the Enabled attribute (the status of Microsoft 365's built-in junk email processing) is reported as True for all users.
  3. Run this command to disable junk processing on each mailbox:
    get-mailbox|set-mailboxjunkemailconfiguration -enabled $false
    This command sets the Office Junk Mail folder to False for all of the user mailboxes, including shared and service mailboxes. 

Microsoft 365 Partner Connector Setup

To prevent IP addresses from being waitlisted during campaigns, all clients using Microsoft 365 must create a partner connector that includes IP addresses from the Security Awareness Training allow list document.

For your Microsoft 365 partner connector:

  1. Select Use the sender’s IP address and enter the following IP range:

  2. Ensure that Reject email messages if they aren’t sent over TLS is selected.
  3. Save the partner connector.

Allowing by IP Address in Microsoft 365 – Modern View

The following steps are for Microsoft 365 Modern View. See the next section for Classic View. 

To set up your allow list:

  1. In Microsoft Defender go directly to the Anti-spam policies page using (You can also start at at and navigate to Email & Collaboration > Policies & Rules > Threat policies > Anti-spam in the Policies section.)
  2. On the Anti-spam policies page, select Connection filter policy (Default) from the list by clicking anywhere in the row other than the check box next to the name.

  3. In the policy details flyout that opens, use the Edit links to modify the policy settings.

  4. Optional: In the Description section, select Edit description and enter a description for the policy in the Description box of the Edit name and description flyout that opens. You can't modify the name of the policy. Click Save.

  5. In the Connection filtering section, select Edit connection filter policy.

  6. In the flyout that opens, add the IP addresses into the Always allow messages from the following IP addresses or address range field. This setting is the IP Allow List. Repeat this step as many times as necessary. To remove an existing entry, click X next to the entry.

  7. When you're finished, click Save.
  8. Back on the policy details flyout, select Close.

  9. To avoid spam filtering, see the Bypass Spam Filtering and the Clutter Folder section below.

Allowing by IP Address in Microsoft 365 - Classic View

The following steps are for Microsoft 365 Classic View. See the above section for Modern View.

To set up your allow list:

  1. Log into your Microsoft 365 Admin Portal. Under Apps, go to Admin.
  2. Under Admin Centers, select Exchange.
  3. In the Protection section, click Connection Filter.
  4. Click the pencil icon msPencil.png to edit the default Connection Filter policy. 
  5. In the IP Allow List, click the plus sign to add an IP address.
  6. Enter the IP addresses listed at the beginning of this article.
  7. Click OK, then click Save.  
  8. See the next section to bypass spam filtering and the clutter folder.

Bypass Spam Filtering and the Clutter Folder

When allowing email by IP Address in Microsoft 365, it's a good idea to create a rule to avoid spam filtering and the clutter folder.

  1. Navigate to Admin > Mail > Mail Flow.
  2. Under Mail Flow > Rules, click the plus button and select Create a new rule...
  3. Provide a name for the rule.
  4. Make selections to create this logical statement: Apply this rule if... The Sender... IP address is in any of these ranges or exactly matches.
  5. Specify the IP addresses listed at the beginning of this article, then click OK.

    • If you are using Barracuda Email Gateway Defense IP addresses and, you can find more information about them here.


  6. On the Modifying the message properties page, under Do the following, click Add action, click Modify the message properties, then Set a Message Header.
  7. Set the message header X-MS-Exchange-Organization-BypassClutter to the value true. Click OK
    Note that both of these values are case-sensitive.
  8. Back under Do the following, select Modify the message properties
  9. Select Set the spam confidence level (SCL) to, then select Bypass Spam Filtering.
  10. Click Save

Microsoft 365 Defender

Microsoft 365 Defender often blocks phishing messages, including legitimate, simulated phishing attacks used for training from Barracuda. You can configure it to allow campaign emails and avoid machine clicks on links within campaign emails. 

For additional information and full instructions, refer to Using Microsoft 365 Defender with Security Awareness Training.

Microsoft Edge Browser

The Edge browser may block Security Awareness Training campaign landing pages. To learn more and prevent this from occurring, see Preventing the Microsoft Edge Browser from Blocking Landing Pages.

Google Safe Browsing Initiative

This Google policy might block Security Awareness Training phishing domains that you want to use in your campaigns. 

To remove this Google block on one or more Barracuda phishing domains, add the blocked domains to the SafeBrowsingAllowlistDomains parameter of Chrome's Enterprise Policy configuration.

For full instructions, refer to Disabling Google Safe Browsing Warning Message Using Group Policy.

Additional Best Practices

The following sections describe additional methods of optimizing your setup of Security Awareness Training, but they are not required.

Landing Page Server Allow List

When users click a link within a campaign message, they are directed to an HTTP or HTTPS Landing Page server. The IP addresses of the Landing Page servers include those in this range:


You can also allow based on the domain name used for each campaign.

Administrative Web Application Allow List

Administrative functions are available using encrypted SSL/TLS at hosted at one of the IPs in the following address range:


We strongly recommend you use Single Sign-On (SSO) for all administrative users.

Educational Content and Survey / Content Delivery Network Allow List

Barracuda's Security Awareness Training servers are located in the Midwest region of the United States. With our worldwide customers, there is always a concern about reducing latency and bandwidth delays when showing educational videos. To solve that, Barracuda  can distribute the read-only multimedia content using a reputable Content Delivery Network (CDN). For security reasons, training content is only delivered via HTTPS.
To create an allow list for educational content and surveys, use the following:


  • https://*



    Note: The CDN option is only used to distribute the Image Gallery components including MP4, WEBM, JPG, GIF, and similar file types. Barracuda recommends you allow list requests and responses for static multimedia content only. The web application and data collection are exclusively performed on the Security Awareness Training servers even with the CDN option.


Using web proxies or content caching interferes with the normal communication between the user and the LMS (Learning Management System) and can result in data inaccuracies. 

To avoid this issue, add the entries in this section to the allow list for the web proxy and exclude them from caching. Add either one of the following lists of entries:


  • https://*






Landing Page “Enable Local IP Detection”

There are two methods to enable detection of the local/non?natted IP address of a browser.

Enable Local IP Detection

To enable JavaScript/Java Local IP Detection Logic, navigate to Campaigns > Landing Pages > Landing Page Manager, and select the Enable Local IP Detection check box. Note that this setting is disabled by default to minimize the chances that users would receive JavaScript, Java, or other errors/warnings on landing pages.  

When you enable local IP detection, each web page might attempt to create a WebRTC connection using Be advised that Barracuda does not control this server. Upon request, Barracuda can provide firewalled access to our hosted stun/RFC 3489 service. If you choose to block access to any/all stun services, the other techniques will be attempted, such as using a custom Java applet. This technique can help augment the data collected for Portable Media Campaigns, where no user information can be associated with the Smart Attachment.


If you do not want to Enable Local IP Detection on a landing page, you can use industry-standard X_FORWARDED_FOR headers. Configure your proxy/NAT firewall to provide these headers. Depending on your network and risk environment, you might be able to configure it to selectively send those headers to the Barracuda web servers rather than sharing with all sites.

Mail Transport Routing

Barracuda strongly recommends a direct mail connection to your email server. This eliminates issues with antivirus/antispam filtering services. These filtering services can cause false clicks or block mock phishing emails entirely if they are not configured properly to allow the emails coming from the Barracuda email servers. Using a mail transport to directly route emails from the PhishLine email servers to your mail server eliminates these issues. To implement mail transport routing, Barracuda needs direct access to TCP port 25 on your email server's external IP. This usually requires a new firewall rule on your company firewall that allows this direct connection. The only other requirement is to provide Barracuda with your mail server’s public host name or public IP address.

Email Address Allow List

You might also combine the above allow list techniques with email account-specific rules based on the addresses used to send out each campaign. For example, you might choose to add to your safe senders list using Group Policy to facilitate delivery of campaign emails directly to user inboxes. Be sure to combine this type of allow listing with IP/DKIM/SPF allow listing. You do not want to allow list a domain or account only to open the door to real attackers. It is also a best practice to disable all allow list settings upon campaign completion.

Gmail Customers

Refer to this support link. 

As a Google Workspace administrator, you can help ensure that messages received from specific sending IP addresses do not get marked as spam. Do this by adding the addresses to an email allow list in your Google Admin console. When you create an email allow list for your Google Workspace account, it affects your entire domain. You cannot create email allow lists that apply to specific organizational units. See other settings you might use instead.

Other Usage Considerations
  • Malicious Code: Barracuda will never intentionally send you malware. Therefore, there is no reason to ever allow list antivirus or other malicious code filters. It is an important layer of protection you should keep in place.
  • Timing: If you are using domain-based or email-account-based allow listing, you will likely want to limit those to the duration of your campaign. Otherwise, you could enable real attackers to misuse your allow list in the future.
  • Domain Name: Each campaign lists the domain names that will be used to deliver your campaign content. Some administrators prefer to allow list by domain instead of IP. Be sure to take measures to prevent real attackers from exploiting those allow listed domain names for real attacks.
  • Email Accounts: Each campaign lists all of the email accounts that will be used to deliver your campaign content.
  • Web Pages: Each campaign lists the web page servers. If you choose to use the Content Delivery Network acceleration for Multimedia Content, you must add as a domain name.
  • Message Content: Many filters examine actual message content. Within the message template editor, Security Awareness Training also provides a spam filtering score based on a popular antispam solution. To ensure delivery of messages, each campaign allows you to send test emails, so you can test the delivery of the messages and replies, while also confirming that the landing page links work.
Additional Help

If you have any questions about using allow lists, contact Barracuda Technical Support.

You can also allow list Security Awareness Training for Barracuda Email Security Gateway.