How to insert text in email body?

[Grace Yin]

Hi,

I saw the message below in red inserted to my email when the recipient replied my email.  I want to know how they did it and if  Office 365 can do it if there is links and attachments in the email.  

ATTENTION: This email was sent to (company name) from an external source. Please be extra vigilant when opening attachments or clicking links.

Need help!

Thanks in advance! 

[#2 · Accepted solution]

Yes you can do this in Exchange on premise or in the cloud using transport rules.

https://docs.microsoft.com/en-us/Exchange/security-and-compliance/mail-flow-rules/disclaimers-signat...

[#3]

Thank you Geoffrey!