A message that is encrypted by Microsoft 365 Message Encryption is delivered to a recipient’s inbox just like any other email message. If the recipient has Outlook 2016 and a Microsoft 365 email account, they'll see an alert about the item's restricted permissions in the Reading pane.

Encrypting an email message in Outlook means it's converted from readable plain text into scrambled cipher text. Only the recipient who has the private key that matches the public key used to encrypt the message can decipher the message for reading.

If you receive a protected email message sent to the work or school account you use with Microsoft 365 in Outlook or Outlook on the web, the message should open like any other message. You'll see a banner at the top of the message that informs you of any restrictions on the message.

Register the password reset verification method for a work or school account. If you forgot your work or school password, never got a password from your organization, or have been locked out of your account, you can use your security info and your mobile device to reset your work or school password. Your administrator must turn on this feature ...

Outlook add-ins and COM add-ins are programs that run within Outlook and perform actions that Outlook doesn't provide. For example, if you use a password management service or an online meeting service, including Skype, you may have an Outlook add-in assisting you.