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The end of an era? Why Apple decided to stop support for Mail plugins

Find out why Apple is ending support for Mail plugins in macOS Sonoma. Uncover the impact on users and developers, and the future of email clients.

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    By Tobias

    After his studies in industrial engineering at RWTH Aachen University, Tobias co-founded Mailbutler GmbH together with Fabian in 2015. In his free time, he spends most of his time in the garden and with his son Timo.

    In the upcoming release of macOS Sonoma on the 26th of September, Apple is set to discontinue its support for external Apple Mail plugins. The company will instead transition to what is referred to as 'extensions', which will exclusively use Apple's somewhat limited MailKit. This marks a significant change in the Apple ecosystem that has sparked extensive conversation, so let's delve into what this means for developers, users, and the future of Apple Mail.

    Solving the problem of the plugin phaseout

    Firstly, the limitations imposed by Apple's MailKit have resulted in a shortage of useful Apple Mail extensions on the market. Without the ability to develop outside of these constraints, developers are challenged to continue providing their services without compromising their functionality. This scenario is particularly problematic for existing Mail plugins, which will now have to navigate the swamp of MailKit restrictions to continue operating.

    Consequently, several developers have decided to alter their course. SmallCubed, known for creating popular plugins such as MailTags, MailAct-On, and SigPro, plans to develop an entirely new email client. This new client promises to deliver the same functionalities as their plugins but will require users to step away from Apple Mail, presenting a significant shift for its current user base.

    In contrast, Mailbutler, arguably the most renowned email plugin, has taken a different approach. Rather than developing a new email client, Mailbutler began making strides a few years ago to reduce its dependency on Apple. It designed general components that operate within the Apple Mail Sidebar and can also function outside of it with minor adjustments. So, while it might not be directly integrated into Apple Mail anymore, Mailbutler aims to operate alongside Apple Mail and provide easy access to all its features. This strategy aims to keep the user experience intact - in fact, improved. More information about Mailbutler's Sonoma compatibility can be found on our blog page.

    Now, let's address the burning question on everybody's lips:

    Why has Apple decided to phase out Mail plugins?

    Primarily, the reason seems to stem from security concerns. Mail plugins are not part of the Mac App Store, meaning they bypass any quality assurance from Apple. As emails often contain highly sensitive information, this is important: It leaves falls to users to ascertain the trustworthiness of plugin developers for themselves. By moving towards extensions and utilizing MailKit, Apple can enforce security measures and standards, ensuring that only safe and reliable applications have access to users' email data.

    However, it's crucial to note that this shift, while made with the best of intentions, has implications for both users and developers. It remains to be seen how this change will shape the landscape of email plugins, extensions, and the overall user experience. As Apple continues to evolve and tighten its ecosystem, we must adapt and innovate alongside it, nurturing an environment of security, functionality, and usability.

    User perspective

    The transition from Mail plugins to extensions and MailKit might initially be jarring for many users, particularly those who have grown accustomed to the customization and flexibility offered by third-party plugins. The change might entail adjustments to user interfaces and/or functionality. However, on the bright side, this move aims to provide users with improved security: Users can be certain the extensions they use are tested and approved by Apple.

    Implications for competition

    This shift has the potential to reshape the competitive landscape. While Apple is striving for a more secure and streamlined ecosystem, competitors like Google's Gmail, which supports a diverse array of extensions, might seize this opportunity to attract users seeking more customizable email solutions. It's a delicate balancing act between customization and security, one that each platform will navigate differently.

    Historical context

    Apple's decision to phase out Mail plugins hasn't come out of the blue, but echoes the company's broader approach toward creating a tightly controlled ecosystem. Previously, Apple moved from kernel extensions to system extensions for similar reasons: Improved security and stability. While this move was initially met with resistance, it has since been largely accepted and appreciated by the community. It remains to be seen whether the shift from plugins to extensions will follow a similar path.

    The future of Apple Mail 

    While we can only speculate about Apple's long-term plans, it's clear that the company is aiming for a more secure and controlled ecosystem. It's conceivable that Apple is working towards integrating more functionalities within its Mail system, thus reducing the need for third-party extensions.

    Specific limitations of MailKit

    Although we mentioned the limitations of MailKit, it's worth diving a little deeper. For instance, MailKit restricts developers from accessing certain elements of the Apple Mail interface, which may limit their ability to offer comprehensive functionalities that were previously possible with plugins. Despite these limitations, Apple believes that enhanced security measures and standard enforcement will outweigh any potential drawbacks.


    As the narrative of Apple Mail continues to unfold, both users and developers alike will need to navigate this new terrain, balancing the trade-offs between security, functionality, and customization. It's the end of an era indeed, but as always, that means it's the beginning of a new one.

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