With the increase of cybercrime incidents, security and privacy of emails has become a major concern for all. Microsoft understands this scenario very well. That’s why it has provided an email encryption option in MS Outlook
To encrypt Outlook emails, you have to follow the steps (applicable to Outlook for Office 365 Outlook 2016, Outlook 2013, Outlook 2010, and Outlook 2007 versions):
While composing an email in Outlook, click File>Properties.
Now select Security Settings from this wizard.
Mark the checkbox Encrypt message contents and attachments then click OK.
To encrypt all your outgoing emails, follow the steps:
In Outlook click File > Options.
In the Outlook Options dialogue box, click Trust Center>Trust Center Settings
Now in Email Security tab, mark the checkbox of Encrypt contents and attachments of all Outgoing messages and click OK.
To open an encrypted email or its attachment, you need a private key. Otherwise, you will get the error messages:
"This item cannot be displayed in the Reading Pane. Open the item to read its contents."
Also, when you click the item you may get:
"Sorry, we're having trouble opening this item. This could be temporary, but if you see it again you might want to restart Outlook.
Your Digital ID name cannot be found by the underlying security system."
But with the private key, you can open these emails without any difficulty.