Mimecast - URL Protection User Guide

Creation date: 10/8/2025 3:26 PM    Updated: 11/18/2025 1:42 PM

Mimecast - URL Protection User Guide


As part of our ongoing focus on security, we’ve enabled a new feature in our email security platform, Mimecast, that may occasionally require your attention. This feature is designed to increase your awareness of potentially harmful content embedded in emails, including malicious links found in attachments.

Additionally, it provides another layer of protection by scanning links for malicious content and warning users upon clicking. Please note: this will only affect emails coming from outside the company into the company. Emails sent internally or to recipients outside the company should not be affected.


What do You need to do?

The next time you click a link in an email, you’ll be asked to enroll your device to continue.

When prompted in the browser, enter your work email address and click Get Authentication Code. You’ll receive a one-time code by email(From: Postmaster@calark.com) to enter into your browser where indicated.

You’ll be asked to enroll once on each device that you use your work email to access (e.g. laptop and mobile). Bear in mind, you’ll need to enroll any new devices, or if you delete your browser cookies.



What this means for you

URL's/links will no longer point to their original destination. They will now point to Mimecast. 


You will however still be able to see the domain that the link would take you to.
In the example above, “Domain=Support.calark.com”, we can see that it would take us to a webpage under the domain Support.calark.com.

Mimecast scans the URL once when the email is first delivered to you, and again when you click the link.
If the scan results come back clean, Mimecast will forward you to the webpage.
If the scan results indicate a potential threat, Mimecast will display a warning and let you know that proceeding may be risky. You would then need to manually accept the risk to continue to the site.

Example of a clicked URL that failed Mimecast scans


Integrated training and awareness opportunities

For a small percentage of links that you click on in emails, you’ll be shown a page with information about the website you’re trying to access.

You’ll be asked to decide if you’re happy to continue to the website, or if you want to change your mind. By prompting you to think before you click, you can help to strengthen our defenses. Look out for useful Safety Tips shown throughout these pages, and click the Previous or Next links to view more.

Please note: the training uses the actual link you clicked on for the training exercise



Important Reminder

Mimecast is a powerful security tool — but it is not a safety net that guarantees every link or attachment is safe.
You are still the most important line of defense against phishing and malicious content.

Even with Mimecast protection in place:


  • Do not click links or open attachments unless you are certain the sender is legitimate and the message makes sense.

  • Be skeptical of urgent or unexpected requests, even if they appear to come from known contacts.

  • Always verify the sender’s address and hover over links to review the true destination before clicking.



Why this change?

A single bad click on a URL can silently compromise your account, giving malicious actors access to your personal information, company data, and even customer data.
These attacks often happen instantly and without any visible sign — by the time you realize something is wrong, the damage may already be done.