Skip to McMaster Navigation Skip to Site Navigation Skip to main content
McMaster logo

Email Caution Banners

Introduced in June 2023, email caution banners increase your email security and protect you from potential hackers and phishing attempts.

Phishing emails often appear to come from internal senders and prompt recipients to click on malicious links or attachments. Email caution banners will appear at the top of any emails that may have originated from outside McMaster University’s systems and serve as a reminder to be extra cautious when dealing with links and attachments.

Here is how the banner will appear at the top of your email:

Caution: External Email

*The banner may appear differently depending on what device you are using and your Microsoft Outlook display settings. 

After the new measure is put into action, ongoing assessments will be conducted to ensure its effectiveness and address concerns that may arise.


The caution banner does not necessarily indicate that an email is unsafe. However, you should be cautious of clicking on any links or opening attachments if you do not recognize the sender. 

There are number of resources available online with more information on how to protect yourself against phishing and scam emails, including:

Email caution banners are applied to most emails that do not end in However, some of these emails be delivered without an external email banner. In these cases, it is recommended that you remain cautious with any links or attachments in the message until you verify the sender.  

No. The email caution banner is designed to help protect the McMaster community from phishing attempts. This is a system-wide measure that will be applied to all users in the email environment and cannot be adjusted by individual users. 

No. The email caution banner cannot be removed from the preview window on Outlook. 

The banner may appear on emails sent through external email programs.

If you have any additional questions or require assistance with your McMaster email, please contact the UTS Service Desk.