Thunderbird for Android should support UnifiedPush

[nathanzachary]

https://unifiedpush.org/

"UnifiedPush is a decentralized push notification system that lets you choose the service you want to use. It’s designed to be privacy-friendly, flexible, and open — making it perfect if you want control over your push notifications."

Currently, Thunderbird for Android relies on Google FCM (Firebase Cloud Messaging) for push notifications.  For users who do not have any ties to Google at all (meaning no GApps installed), there are currently no options for push notifications within Thunderbird.  UnifiedPush has several implementation apps (such as ntfy, Sunup, et cetera) making it easy to set up push notifications as long as the app itself supports integrating with a push distributor.

This was discussed via a GitHub issue starting back in 2021, but the issue was locked without much explanation (outside of some potentially misinformed talk of needing a proxy server):

https://github.com/thunderbird/thunderbird-android/issues/5165

[Jon]

Thanks for submitting an idea to the Mozilla Connect community! Your idea is now open to votes (aka kudos) and comments.

[Ponda]

I'm moving away from Google Android this year, so I will need it. Similar idea for Firefox(?) here.

[rtonholo]

Hi there! Rafael here, one of the developers on the Thunderbird for Android team.

Thanks for bringing this idea up. I want to clarify one important point first:

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@nathanzachary wrote:

Currently, Thunderbird for Android relies on Google FCM (Firebase Cloud Messaging) for push notifications.  For users who do not have any ties to Google at all (meaning no GApps installed), there are currently no options for push notifications within Thunderbird. 

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Thunderbird for Android does not use FCM/Firebase Cloud Messaging for mail notifications.

What the app currently calls "Push" is IMAP IDLE support. When an account and folder are configured for push, Thunderbird keeps an IMAP connection open to the mail server, where the provider supports IMAP IDLE. When the server reports that the folder has changed, the app syncs and then posts a local Android notification if there is new mail.

That means Thunderbird for Android's current mail notifications do not depend on Google Play Services, GApps, or FCM. They can still be affected by the mail provider's IMAP IDLE support, account/folder settings, and Android's background/battery restrictions, but Google's push infrastructure is not part of this notification path.

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@nathanzachary wrote:

This was discussed via a GitHub issue starting back in 2021, but the issue was locked without much explanation (outside of some potentially misinformed talk of needing a proxy server):

https://github.com/thunderbird/thunderbird-android/issues/5165

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The proxy/server point is not a misunderstanding; it is the key technical issue for making UnifiedPush work with arbitrary email providers.

UnifiedPush solves the delivery part of push notifications: a server sends a push message to a distributor chosen by the user, and the distributor delivers it to the app. But for email, Thunderbird still needs something server-side to know that new mail has arrived and to send that push message.

For Thunderbird to support UnifiedPush for email, one of these would need to exist:

1. The user's email provider would need to offer a server-side push mechanism that lets Thunderbird register a device/app endpoint and receive new-mail events. That would likely require provider-specific APIs, credentials, and registration/unregistration flows, so it would not be a generic solution for all IMAP providers.
2. For providers that do not offer such a mechanism, there would need to be a bridge/proxy service that logs in to the user's mailbox, watches it — for example via IMAP IDLE — and sends a UnifiedPush notification to the phone when new mail arrives.

The second option is the "proxy server" point from the older GitHub discussion. It may be possible for a user to self-host something like that, but it has serious security and privacy implications if Thunderbird were to operate it as a service, because such a service would need access to users' mailboxes or account tokens. That is not a role we are comfortable taking on.

So the correction is: Thunderbird for Android's current mail notifications are not delivered through FCM and do not require Google Play Services or Google apps to be installed. A device without GApps can still receive mail notifications, provided the account/server supports IMAP IDLE and Android allows the app to run in the background.

UnifiedPush could be useful in cases where a mail provider, or a user-controlled bridge, already supplies new-mail push events. But adding UnifiedPush support to the app alone would not replace the current IMAP IDLE approach for arbitrary email accounts.