Pretty Good Privacy (PGP) is an encryption program that provides cryptographic privacy and authentication for data communication. PGP is used for signing, encrypting, and decrypting texts, e-mails, files, directories, and whole disk partitions and to increase the security of e-mail communications. Phil Zimmermann developed PGP in 1991.
An email client, email reader or, more formally, message user agent (MUA) or mail user agent is a computer program used to access and manage a user's email.
Hushmail is an encrypted proprietary web-based email service offering PGP-encrypted e-mail and vanity domain service. Hushmail uses OpenPGP standards. If public encryption keys are available to both recipient and sender, Hushmail can convey authenticated, encrypted messages in both directions. For recipients for whom no public key is available, Hushmail will allow a message to be encrypted by a password and stored for pickup by the recipient, or the message can be sent in cleartext. In July 2016, the company launched an iOS app that offers end-to-end encryption and full integration with the webmail settings. The company is located in Vancouver, British Columbia, Canada.
S/MIME is a standard for public-key encryption and signing of MIME data. S/MIME is on an IETF standards track and defined in a number of documents, most importantly RFC 8551. It was originally developed by RSA Data Security, and the original specification used the IETF MIME specification with the de facto industry standard PKCS #7 secure message format. Change control to S/MIME has since been vested in the IETF, and the specification is now layered on Cryptographic Message Syntax (CMS), an IETF specification that is identical in most respects with PKCS #7. S/MIME functionality is built into the majority of modern email software and interoperates between them. Since it is built on CMS, MIME can also hold an advanced digital signature.
End-to-end encryption (E2EE) is a private communication system in which only communicating users can participate. As such, no one, including the communication system provider, telecom providers, Internet providers or malicious actors, can access the cryptographic keys needed to converse.
Email privacy is a broad topic dealing with issues of unauthorized access to, and inspection of, electronic mail, or unauthorized tracking when a user reads an email. This unauthorized access can happen while an email is in transit, as well as when it is stored on email servers or on a user's computer, or when the user reads the message. In countries with a constitutional guarantee of the secrecy of correspondence, whether email can be equated with letters—therefore having legal protection from all forms of eavesdropping—is disputed because of the very nature of email.
The following tables compare general and technical information for a number of notable webmail providers who offer a web interface in English.
DomainKeys Identified Mail (DKIM) is an email authentication method designed to detect forged sender addresses in email, a technique often used in phishing and email spam.
Opportunistic TLS refers to extensions in plain text communication protocols, which offer a way to upgrade a plain text connection to an encrypted connection instead of using a separate port for encrypted communication. Several protocols use a command named "STARTTLS" for this purpose. It is a form of opportunistic encryption and is primarily intended as a countermeasure to passive monitoring.
Email encryption is encryption of email messages to protect the content from being read by entities other than the intended recipients. Email encryption may also include authentication.
Secure messaging is a server-based approach to protect sensitive data when sent beyond the corporate borders, and it provides compliance with industry regulations such as HIPAA, GLBA and SOX. Advantages over classical secure e-mail are that confidential and authenticated exchanges can be started immediately by any internet user worldwide since there is no requirement to install any software nor to obtain or to distribute cryptographic keys beforehand. Secure messages provide non-repudiation as the recipients are personally identified and transactions are logged by the secure email platform.
Outlook.com, formerly Hotmail, is a free personal email service offered by Microsoft. This includes a webmail interface featuring mail, calendaring, contacts, and tasks services. Outlook can also be accessed via email clients using the IMAP or POP protocols.
Jon Callas is an American computer security expert, software engineer, user experience designer, and technologist who is the co-founder and former CTO of the global encrypted communications service Silent Circle. He has held major positions at Digital Equipment Corporation, Apple, PGP, and Entrust, and is considered "one of the most respected and well-known names in the mobile security industry." Callas is credited with creating several Internet Engineering Task Force (IETF) standards, including OpenPGP, DKIM, and ZRTP, which he wrote. Prior to his work at Entrust, he was Chief Technical Officer and co-founder of PGP Corporation and the former Chief Technical Officer of Entrust.
Fastmail is an email hosting company based in Melbourne, Australia. In addition to its Fastmail-branded services, the company also operates Topicbox, a mailing list service, and Pobox, an email service it acquired in 2015.
Proton Mail is a Swiss end-to-end encrypted email service founded in 2013 headquartered in Plan-les-Ouates, Switzerland. It uses client-side encryption to protect email content and user data before they are sent to Proton Mail servers, unlike other common email providers such as Gmail and Outlook.com. The service can be accessed through a webmail client, the Tor network, Windows, macOS and Linux (beta) desktop apps and iOS and Android apps.
Threema is a paid cross-platform encrypted instant messaging app developed by Threema GmbH in Switzerland and launched in 2012. The service operates on a decentralized architecture and offers end-to-end encryption. Users can make voice and video calls, send photos, files, and voice notes, share locations, and make groups. Unlike many other popular secure messaging apps, Threema does not require phone numbers or email addresses for registration, only a one-time purchase that can be paid via an app store or anonymously with Bitcoin or cash.
Tuta, formerly Tutanota, is an end-to-end encrypted email app and a freemium secure email service. The service is advertisement-free; it relies on donations and premium subscriptions. As of March 2017, Tutanota's owners claimed to have over 2 million users of the product.
Autocrypt is a cryptographic protocol for email clients aiming to simplify key exchange and enabling encryption. Version 1.0 of the Autocrypt specification was released in December 2017 and makes no attempt to protect against MITM attacks. It is implemented on top of OpenPGP replacing its complex key management by fully automated exchange of cryptographic keys between peers.
Proton AG is a Swiss technology company offering privacy-focused online services. It was founded in 2014 by a group of scientists who met at CERN and created Proton Mail. Proton is headquartered in Plan-les-Ouates, Switzerland. It is supported by FONGIT and the European Commission.
mailbox.org is an encrypted email service provider based in Germany. The encryption system uses PGP like most other encrypted email providers. It also features address books, calendars, video conferencing, online office and tasks management. It competes against Office365 and GSuite as a German based provider. Its target customers include private, business, school and public authorities.
