Friday, November 17, 2023

Mail Extension Postmortem

Tucky Wong:

While Daylite, including the Daylite Mail Assistant, is compatible with macOS Sonoma, we strongly recommend that you hold off on upgrading to Sonoma at this time.

Our recommendation is based on feedback from early adopters, which has highlighted a potential significant interruption in your current email workflows. Additionally, we are actively addressing certain issues in the extension API to ensure a smoother transition.

Apple Mail is crashing when using various Mail extensions. Now that no third-party code can run within the Mail process, it’s straightforward to attribute this to a Mail bug. However, unlike with plug-ins, it’s no longer possible to patch Mail to work around such a bug or to try to catch an error or use a different API to avoid triggering it. All we can do is report the bugs to Apple (or not) and wait.

Fortunately, I have not seen any Mail crashes related to the SpamSieve extension. Perhaps this is because it’s using a different extension point. However, it’s now clear that, despite MailKit being an officially supported API, Mail extensions are far less reliable than Mail plug-ins were. Bug reports seem to receive no more attention than before.

SpamSieve continues to offer a Mail extension, since it’s helpful when it works, but my focus since WWDC has been on reimplementing SpamSieve’s Apple Mail support—again—so that it doesn’t have to rely on the Mail extension at all. With SpamSieve 3.0, you had to manually enable a workaround if Mail stopped communicating with the extension. With 3.0.1, SpamSieve could enable the workaround automatically, but (due to problems with Mail’s AppleScript support) it could be slow or not work at all for mailboxes containing many thousands of messages. With 3.0.2, it’s where I want: fully automatic and fast, even when Mail malfunctions.

Tobias Knobl:

Apple’s recent updates no longer allow us to use the embedded sidebar in Apple Mail. But fear not, because we’ve come up with a solution – the Floating Sidebar.


With the changes to macOS Sonoma, we can no longer display tracking check marks in the message list. The email tracking information is now accessible in the Mailbutler Sidebar, right next to your email.


You may have noticed something different in your Apple Mail: a seemingly strange and technical string of characters appearing in each email. This is known as the “Message-ID,” a unique identifier generated for every email message.

I guess they have to read this from another process to know which message Mail is displaying.

Fabian Jäger:

As we are not able to adjust the behavior of Mail itself, we needed to find new ways of still being able to adjust the emails our users send out to include the functionality that they expect when using Mailbutler.


Mailbutler’s Mail Bridge acts like an additional, local SMTP service that takes care of enriching outgoing messages with features, such as email tracking, and afterwards handing it over to the actual SMTP server for final delivery. Thus, all outgoing emails take another step between Mail as the sending email application and the regular SMTP delivery service.


8 Comments RSS · Twitter · Mastodon

Hi, Michael,

Since you are an expert in the area of Apple Mail app, maybe you could shed some light on a problem I am having with Mail since I bought a new Mac with Ventura (previously, I had an old MacPro with Mojave and Mail was working as expected).

My problem is that I can not effectively block some spam messages from reaching my inbox. Not only that, but also those messages are re-appearing in my inbox after I manually deleted them. I have a rule in my Mail settings that instructs Mail to delete spam immediately. That rule does not work, either.

Would you care to comment on that, please?

@Rob It’s unclear, but I typically hear about problems like that when the Trash mailbox is configured to be stored locally rather than on the mail server. Mail (since Catalina or so) is more reliable at moving messages within the same server.

Thank you, Michael. I am going to reconfigure the trash mailbox.

Have you encounter the issue with some mailing lists whose addresses can not be blocked in Mail? That is so annoying...

@Rob No. If you mean “blocked by SpamSieve” please contact technical support.

No, I do not have your SpamSieve yet, but I will definitely give it a try. Maybe that's all I need to rid Mail of those problems?

Incidentally, I have used SpamSieve for a while in the past (maybe 15 years ago), but then Mail got much better at handling spam, so SpamSieve became a victim of neglect while upgrading Macs and operating systems.

I purchased SpamSieve (together with EagleFiler) and now spam messages are correctly moved to spam folder. I just wish I could block some notorious spammers, or at least delete them immediately instead of moving them to spam folder.

BTW, EagleFiler requires Rosetta to be installed. For now, I am postponing installing EagleFiler until it will be a native app in Ventura. Is there a chance for that to happen in near future?

@Rob You can use the Move it to the Trash if the spam score is at least setting to have SpamSieve move the most spammy messages directly to the Trash, so that they’re separate from the regular spam in the Junk mailbox.

A native Apple Silicon version of EagleFiler should be ready later next year, but it runs great in Rosetta so I don’t see any reason to wait on installing it.

The latest information from Daylite; supporting Outlook as an alternative looks rather desperate to be honest:

I'd like to take a few moments to update you on the state of Daylite Mail Assistant on macOS Sonoma and discuss where we are, how we got here, and the roadmap moving forward.

When Apple announced the end of Mail Plugins in Sonoma and provided us with an improved Mail Extension API, we were excited. It meant improved security and made keeping up with Apple's yearly OS refresh easier. Regrettably, our excitement did not match reality. Since Sonoma's release, issues have arisen related to usability and stability, causing us to no longer recommend Sonoma for anyone using the Daylite Mail Assistant.

If you have already updated Sonoma and are experiencing issues, I am truly sorry we did not communicate effectively about these sooner, and I take full responsibility for this lapse in communication. We are working to get these solutions out to you ASAP.

Now, allow me to outline the issues and how we are progressing on addressing them:

Usability: Removing the sidebar in Mail has made using the Daylite Mail Assistant more challenging, as it takes more clicks to link your emails. While this new popover is what all Mail Extensions are limited to, it's become clear that it is not good enough. To address this issue, we are working on a way to present Daylite Mail as a floating window that works in a very similar way to the Legacy Daylite Mail Assistant Plugin’s sidebar. We have been working on this solution, and we will begin a beta soon. If you want to be involved with the beta, sign up for the waiting list.

Daylite Mail Disappearing: Under certain circumstances, the Daylite Mail Assistant will disappear from Mail without warning. A quick fix for this is to quit and relaunch Apple Mail. Addressing this bug has been a top priority, with our latest update reducing these instances by 74%, and we've been continuing to work to eliminate the remaining causes.

Apple Mail Crashes: One of the key advantages of Apple's Extension frameworks is that the extensions cannot crash an application. Despite this, developers for Mail Extensions like us have reported Apple Mail crashes that seem to be related to the extension support itself within Apple Mail.

These issues ultimately rely on Apple to fix, and while we have filed reports, we are not relying on this alone. We have been developing Daylite Mail for Outlook. Outlook is free and can work with the same types of accounts as Apple Mail. If you want to be involved with the beta, sign up for the waiting list.

Whether you are waiting to update Sonoma or have and are experiencing these issues, I am truly sorry for any frustration and disruptions to your business that this has caused you. Your satisfaction is our top priority, and we are committed to regaining your trust.

If you haven't updated yet, please do not update to macOS Sonoma until these issues are resolved. To keep you informed and involved in these improvements, we have created a dedicated page where you can track our progress. Please visit Daylite Mail Assistant on Sonoma Updates for regular updates on the steps we are taking and the progress we are making. Your feedback is invaluable to us, and we want you to feel a part of this process as we work to make things right.

Thank you for your understanding and continued support.

Best Regards,

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