Outlook natively encrypts emails from one mailbox to the recipient utilizing Transport Layer Security (TLS). This essentially protects the content from point to point (mailbox to mailbox). TLS however cannot offer any other forms of protection such as forwarding prevention or content encryption.
In cases where message encryption and protection are required, Outlook offers you the ability to set permissions (called encryption in 0365 clients). When you enable encryption on your email you can stop recipients from forwarding your email, ensure that your email does not leave WSU, validate that your words stay in ‘read only’ mode, or encrypt it so that only targeted individuals can see the content of the email. To access this configuration, click on the ‘permissions’ section of an email and then select the most appropriate permissions. Below will go over the configuration in more detail.
Please note that all this content can be found on online in O365 documentation. Here are some helpful links on the subject:
Levels of encryption
What all emails are natively set to. This setting has no restriction on the email nor its content.
Locks the email to only be visible by those that are recipients.
Do not Forward
Prevents the email from being forwarded.
Encrypts and keeps the email only accessible to those within WSU.
Confidential View Only
Encrypts and keeps the email in read only mode accessible to those within WSU.
Encryption occurs on an induvial email basis and is easy to apply. Simply compose your email and when ready navigate to Options> Permissions (button will be called ‘Encryption’ if you are running on online version of Outlook) and then select the most appropriate level of security needed for the email and its content.
Q: What if I want to send an encrypted email to someone outside of WSU?
A: If the recipient is outside of WSU the individual(s) will be requested to authenticate to see the content via a temporary security code (random set of numbers generated by Microsoft).
Q: Are attachments also encrypted?
A: Yes! Though if the recipient downloads it there nothing stopping them from sending it to someone else.