Mailvelope Upgrades for Webmail Security, Resiliency, and Usability

Browser extension Mailvelope, which provides end-to-end encryption for emails, has fortified its codebase and streamlined onboarding and PGP key queries.
Fri, 2024-05-24 16:33

By Bernhard Spirkl, Mailvelope

A good encryption tool is only as good as its latest updates and its users’ habits. The popular, open-source browser extension Mailvelope has been working since 2012 to make email encryption a more common practice—by making it as easy as possible to encrypt messages sent via webmail services. With its most recent upgrades, Mailvelope has strengthened its security, retooled its architecture, and streamlined the onboarding process for new users.

Mailvelope began when its creators were alarmed by the absence of end-to-end encryption in popular webmail applications. To fill a big gap in this common use case, we designed the tool as a browser extension. Mailvelope utilizes the JavaScript library OpenPGP.js to simplify the encryption and decryption of emails, particularly when accessing popular services like, Yahoo, and Gmail. Though Mailvelope was born in Germany, we often describe Mailvelope as a “Swiss knife” for webmail encryption due to its exceptional adaptability, and seamless functionality across nearly every webmail environment.

Privacy risks and open-source tools are constantly changing, so Mailvelope’s success has always depended on aligning with the digital security ecosystem and helping users get past the perceived complexities of setting up Pretty Good Privacy (PGP) encryption (a program that encrypts and decrypts data for online communication, including emails, files, and directories). We believe the convenience of a browser extension and the integration with common webmail services are a big part of the reason the tool has received widespread adoption in open-source communities over the past decade.

But keeping up with webmail product changes and new security threats is a challenge. Since its earliest days, Mailvelope has received pivotal support from OTF to respond to emerging technical hurdles and evolving user demands. These latest updates have made Mailvelope 5.0 and the subsequent minor releases more resistant to attacks, fully aligned with the latest version of OpenPGP, and better designed to support new users and their most common needs.

Keeping up: Aligning Mailvelope with OpenPGP.js 5.0

OpenPGP.js is a JavaScript library that implements the OpenPGP standard, enabling developers to integrate end-to-end encryption and digital signing into web applications. Its functions include encryption, decryption, digital signatures, and compatibility with other OpenPGP-compliant software. 

Maintaining maximum compatibility with the newest versions of OpenPGP is not simply a “nice-to-have” for Mailvelope. OpenPGP.js is a central pillar of open-source cryptographic standards, and Mailvelope relies heavily on this implementation of the OpenPGP protocol to get its magic done. The release of OpenPGP.js 5.0 required major code changes for Mailvelope to ensure compatibility and reliability. These adjustments helped us to make significant progress in two areas of our extension in particular: in the handling of keys on our own key server, as well as in a user-friendly handling of signatures.

Resiliency: Fortifying Mailvelope Key Server and Enhancing Key Discovery

The exchange of encryption keys is fundamental to email security. Key servers enable users to list and find each other’s public keys (though not their private keys, obviously). When the SKS (short for “Synchronizing Key Server”) network faced a certificate spamming attack in 2019, the community of OpenPGP users acknowledged that the issue was not addressable within the existing SKS framework. The SKS key server network ceased to serve as a viable mechanism for querying keys using email addresses or most other common search methods.

Although Mailvelope already had its own key server at, which was not affected by the attacks, this change in the key server landscape prompted us to think about how we could provide our users with an even more stable and abuse-proof code base. 

As a result of these considerations, it was decided that Mailvelope will, in the future, support not only its own but also the servers and the Web Key Directory (WKD). We are therefore now solely relying on so-called “verifying key servers,” which will check if a certain key entry genuinely belongs to the paired email address, adding an extra layer of security. Our implementation of the abuse-resistant OpenPGP Keystores specification has also fortified the Mailvelope key server against certificate flooding attacks.

In addition to these backend changes, our app includes several updates to its user-facing features. The key search function includes usability enhancements that enable users to search for keys across multiple key servers using email addresses, key IDs, or fingerprints. Once one or more keys are found, users can directly import them into their Mailvelope keyring. These front-end changes are part of a wider set of changes to keep Mailvelope highly usable and highly responsive to feedback from our community.

The new UI of Mailvelope key search

Once a key is found and confirmed, it can be imported directly into the user’s keyring.

Enhancements in Signature Management

With the updates implemented for alignment with OpenPGP.js v5.0, Mailvelope has significantly enhanced its handling of PGP signatures across various functions. Version 5.1.0, which debuted in July 2023, introduced several improvements to signature verification. 

Mailvelope detection of address mismatch

Recognizing the pivotal role of proper signature handling in ensuring secure email exchanges, Mailvelope now shows user-friendly warnings for any detected disparities between sender email addresses and email signatures.

Furthermore, the results of signature verification are now integrated into the file decryption user interface. Previously, this functionality was only available if you used GnuPG as your primary Mailvelope keyring.

Signature verification integrated into decryption UI

To support—and promote—the use of signatures, we have also updated the relevant FAQ sections on our site and posted a Mailvelope blog to help explain the importance of PGP signatures both for securing the privacy of email messages, and for enabling reliable authentication of messages (i.e., that the sender is who you think they are) and for assuring that messages remained free from tampering during transit (i.e., that the package was not intercepted or altered).

Usability: Prioritizing Onboarding and Feedback

With its updated software and user interface, Mailvelope continues its investment in making encryption not just adoptable, but explainable. The more the internet community understands encryption, the more people will embrace the tools and the good habits of email security.

Along with its extensive FAQ section, the Mailvelope website has offered a tutorial to support users in the onboarding process. But we know that people arrive at the site with a wide range of technical needs and expertise levels—from savvy security experts to privacy novices, and from our enterprise clients to our wide base of individual users.

This diversity of users and needs had not been adequately addressed in the Mailvelope tutorials. To help us overcome our own “blind spots” in user guidance, Mailvelope worked with Superbloom (previously known as Simply Secure) to conduct a survey of actual users. Guided by their insights, we restructured the tutorials and FAQs to streamline the experience based on users’ most common questions and their chosen email providers.

Our Get Started section now gives the right advice for each situation users might face and provides information in five languages. We also know how many people just never read “Get Started” pages, so the UX changes to the tutorial are all designed to lower the threshold for those who are onboarding themselves. Because Mailvelope’s staff is small, we want to help new users progress as far as they can in sending a first encrypted email, without waiting for a support reply from us.

The general reaction of the users and the community to these changes has been very positive, and we’ve already observed a measurable decrease in support requests regarding onboarding.

Some of these changes may sound cosmetic, but they help to address a fundamental challenge in digital security: to reduce the asymmetry between those who communicate with strong security and those whose security practices are inconsistent or nonexistent. “Asymmetric encryption” introduces risk in any exchange. The findings in our recent survey reinforced this precept, revealing a user divide between the “persuaders” who embrace and advocate encryption and the “allies,” who seek to adopt good practices but may find the steps to secure their communications too complicated or inconvenient.

Towards the Future and Sustainability

We are grateful to the OTF Internet Freedom Fund for their generous support, which has enabled us to make significant improvements. These enhancements reflect our commitment to staying responsive to the ever-changing landscape of security threats, open-source development, user habits, and decisions made by major browsers and webmail services.

Under the current funding from OTF’s FOSS Sustainability Fund (pilot round), our focus is on achieving greater financial sustainability through the sale of our Mailvelope business products. This follow-on funding allows us to expand our team, which is necessary to offer Mailvelope Business alongside Google Workspace for companies that process their emails on 

In addition to this product expansion, we are also using the funding to fulfill the feature requests of our community. For example, there have been repeated requests for a rich text formatting option in the Mailvelope editor. Another goal is to be able to offer Mailvelope on mobile devices. The technical developments in this area are promising, and we are currently evaluating various strategies and approaches to overcome the limitations of being available only as a browser extension. This would be another important step towards achieving sustainability for Mailvelope in the longer term, as it would open up many new business models that are often in demand.