Microsoft Office 365 E-mail Encryption

What is E-Mail encryption?

Encryption is the process by which information is encoded so that only an authorised recipient can decode and consume the information.


 About encryption in Office 365

With a Microsoft Office 365 E-mail account, you can be assured that your data is protected as it is encrypted while it resides on Microsoft cloud servers and while it’s being transmitted between you and other Microsoft users on the same Domain.

So when you share messages and information with colleagues that have E-Mail accounts with the same suffix, you can be confident that you are working safely.


How does Microsoft use encryption in Office 365?

Microsoft uses encryption in two ways:

By implementing encryption in the Microsoft cloud service

In the service, Microsoft makes use of encryption in their infrastructure platform where it works by default and end users don’t have to configure anything. So information shared between colleagues with the same suffix can be assured that such information exchanges are appropriately secured in transit and equally safeguarded whilst it resides in the Microsoft Office 365 platform.

By offering it as a customer control

As a customer control, Microsoft E-Mail encryption works in the following way:The E-mail message is encrypted, or transformed from plain text into unreadable ciphertext, either on the sender’s machine or by a central server while the message is in transit.The message remains in ciphertext while it’s in transit in order to protect it from being read in case the message is intercepted.Once the message is received by the recipient, the message is transformed back into readable plain text in one of two ways:

  • The recipient’s machine uses a key to decrypt the message, or
  • A central server decrypts the message on behalf of the recipient, after validating the recipient’s identity.


Please be minded that once a secure E-mail has been sent, the E-mail recipient has full control over the information and data held in the E-mail.

So how do I encrypt my E-mail messages in Office 365?

Encrypting an E-mail message in Office 365 is very easy

Simply, type the letter “E” within round parenthesis on the Add Subject line of your Email

For clarification purposes, the round parenthesis can be found above the 9 and 0 on the standard qwerty keyboard

So your messages will be formatted like this….

(E) Did you know that you can encrypt E-mail?

(E) Meeting invitation…




Your E-mail recipient will receive the following message:

Click on the Download link and save the files to any preferred location on the computer.

(Please note that these files do not hold any information embedded in the E-mail message)

Click on message….


….and the following screen will be displayed

Your E-mail recipient will now have two choices to read the message:

Either to select Sign in to sign in with a Microsoft account, or

Select Use a one-time passcode.

If Use a one-time passcode is selected, the recipient will receive the following message:


They must retrieve the passcode from the nominated E-mail account to access the message.

The E-mail will look like this:

The procedures highlighted above ensure that sensitive information and data

never leaves the secure Microsoft Office 365 site


But please remember…. once a secure E-mail has been sent, the E-mail recipient has full control over the information and data held in the E-mail message

And for further guidance on encryption: