We recommend forwarding this article to IT administrators responsible for mailboxes and gateways (e.g. Azure & Mimecast), and internet traffic gateways.

Allow list for browser and app

app.cybsafe.com is the fully qualified domain name in use.

Other external URLs in use:

Allow list for receiving emails

⚠️ To guarantee authenticity all of our emails are sent securely and signed with a DKIM signature. We highly recommend instead of IP based checks that you instead verify our email authenticity via our DKIM and SPF checks in your mail solution.

For mail servers and mail gateways

To make sure our emails reach people, you need to arrange for the following IP addresses and domains to be allow listed in your mail servers:

For more information around this, please click here.

  • Registration, News and Administration – IP / cybsafe.com

Both these IP addresses are dedicated to CybSafe.

If you are using a mail filter, both your email solution and inbound gateway (Filter) need to use allow list rules be allowlisted

For Microsoft 365

To allow the training reminders and simulated phishing emails to reach your people, the CybSafe servers must be allow-listed on your mail platform(s). This is usually either Microsoft365 or an on-premise mail server. If you use an external email scanning service (e.g. FireEye ETP, Mimecast, MessageLabs or Proofpoint), you will also need to allow CybSafe emails on their system. Please consult their documentation for details of how to do this.

Note – the domains “cs-mail-sender.com” and “cybsafe.com” are used in the MailFrom attribute as per RFC 5321, not in the From attribute as defined in RFC 5322. This ensures that even when the “From” address seen in the email does not match – which is the case for phishing emails - the rule will still be applied.

Exchange Online Protection - advanced delivery policy

Exchange Online Protection (EOP) does not allow safe lists or filtering bypass for messages that are identified as malware or high confidence phishing. But, there are specific scenarios that require the delivery of unfiltered messages such as a CybSafe Phishing Campaign.

Follow the steps in this Microsoft article to ensure delivery of our Emails:

Configure the delivery of third-party phishing simulations to users and unfiltered messages to SecOps mailboxes

Microsoft Defender

If your organisation uses Microsoft Defender, you may need to configure settings in it to allow CybSafe phishing emails to be delivered.

Use the Microsoft 365 Defender portal to configure third-party phishing simulations in the advanced delivery policy


If you're using Mimecast Email Security you can allow list CybSafe to permit our simulated phishing emails and training invitations through to your end users.

In this article, "Additional Allowlisting Information for Mimecast", you’ll find instructions for several different policies, which you’ll need to add to your Mimecast console to allow the use of CybSafe.

Still have any questions?

If you still have questions, you can contact the CybSafe team via support@cybsafe.com. We’re on hand to help resolve any further issues!

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