Sending encrypted or protected email is useful when sending sensitive information.  

Google Mail (Gmail) allows you to send an email in Confidential Mode

You can use confidential mode to set an expiration date for messages or revoke access at any time. 

Important: Although confidential mode helps prevent the recipients from accidentally sharing your email, it doesn't prevent recipients from taking screenshots or photos of your messages or attachments. Recipients who have malicious programs on their computer may still be able to copy or download your messages or attachments.

To send a confidential email from Gmail:

1. Open Gmail on your computer or phone.
2. Select 'Compose'.
3. Look for a padlock icon at the bottom of the Compose screen, or click on the three dots to find Confidential Mode.
4. Set an expiration date and passcode.

Read for more information about Confidential Mode Gmail.

Outlook Mail allows you to send an encrypted email. 

 Encryption will require the user to request a passcode in order to open the content of the message.

To send an encrypted email from Outlook:

1. Open Outlook.
2. Select 'New Mail'.
3. Select the Options tab from the top menu.
4. Select the Encrypt Icon (shaped like a padlock).
   
5. Select Encrypt.

Read for more information about Encrypted email in Outlook.