ProtonMail is an end-to-end encrypted email service founded at the CERN research facility in 2014. Its servers are located in Switzerland, that means your data is protected by strict Swiss privacy laws.
ProtonMail uses encryption to encrypt the email contents and user data before they reach the ProtonMail Servers. The mailing service has a free service which offers 500 MB storage and 150 emails to be sent per day while the paid services have much more to offer than the free version.
You can set the expiration time for the email, let it be weeks, days, or hours. So, once you send the email, the timer start and the email will be expired after certain interval. This, however, is only for emails that are sent from ProtonMail accounts to ProtonMail accounts. The expiration time isn’t valid for sending the messages to other email services such as Gmail since they won’t be deleted there.
However, it still offers an encryption option that allows you to encrypt the email that you send to users of other email services. Before you send the message, you can hit the padlock icon and set a password for the email.
The receipt must enter the password in order to open the message. This option along with the expiration feature makes sure that once ProtonMail deletes the message from its servers, it will also be deleted from external servers, making it an encrypted email service,