Other Wiki pages: NGI Proposal

UnifiedPush for email via IMAP WebPush

Instant notifications, but without Big Tech.

Like this...	not this...

This project brings freedom-tech push notifications to mobile email.

Email apps are a priority for wider adoption of UnifiedPush, the standard for independent mobile push notifications. Providers wait for app support, apps wait for server support, but mail servers are diverse.

This project implements:

• an IMAP extension for WebPush support, in one IMAP server;
• UnifiedPush via IMAP-WebPush, in one mobile IMAP client.

The chosen IMAP server and client are likely to be Dovecot (as used in mailcow) and K9-mail (now a Thunderbird project).

The result will:

• demonstrate the feasibility of freedom-tech push notifications for email;
• demonstrate the feasibility of adding it to common existing (IMAP) mail servers;
• provide a proof-of-concept implementation for one server and one client.

This implementation will initially follow a draft specification for IMAP WebPush Extension. This work may support and inform an update to that spec.

As a side effect, adding web push to an IMAP server could potentially also benefit web mail applications.

The text above is part of the NGI Proposal. The following sections are additional.

Rationale

UnifiedPush frees people from dependence on Big Tech's services for their push notifications, giving a choice of push service provider. Adoption in the freedom-software mobile ecosystem is constrained by the common chicken-and-egg problem: app developers wait for support by their OS and service provider (even though power users don't need it ¹); OS and service providers wait for apps. Any progress to break the circle is helpful.

Email is one of the more important and more difficult classes of apps to target. The majority of mail servers now use IMAP, and the IMAP-IDLE technique for push. Only a few email servers and clients so far implement the newer JMAP protocol suite which supports WebPush on the server side and so enables apps to use UnifiedPush. This route to upgrading any existing IMAP email client is therefore high effort (implementing JMAP) and low reward (few servers support it) for app developers, and similarly for server developers.

If more IMAP servers would be able to support WebPush, that would enable email apps to get their push notifications through UnifiedPush. Adding that support into an existing IMAP email client would then be easier (a small change). Similarly, for IMAP server software and operators, adopting the extension would be easier (a small change). Together, these additions may result in more servers and clients more easily adopting UnifiedPush, and so making the system more attractive to others.

Risks

Many email servers, probably most, are unlikely to adopt a new extension, in the short term. The email server landscape is wide, deeply rooted, conservative, and dominated by proprietary services, even if using some open source software. However, there are some classes of servers that most likely would, mostly in freedom-software.

Even a modest increase in server support might be expected to enable a more than proportionate increase in client support.

References

UnifiedPush:

• UnifiedPush -- source
• #unifiedpush:matrix.org, #unifiedpush-dev:matrix.org, #unifiedpush-space:matrix.org
• Email UnifiedPush proxy #19 (UP wish list)

Standards:

• COI: IMAP WebPush Extension v1.0 draft spec (archived), proposal to align with JMAP RFC8620
• JMAP PushSubscription standard
• DeltaChat standards ("Push: IMAP IDLE")
• WebPush standard (MDN)

Prominent email apps:

• lttrs-android supports UP via JMAP WebPush
• DeltaChat -- source -- other clients
• K9-mail -- source -- closed issues -- JMAP request -- wishlist (this is not on it)

Email servers:

• mailcow (contains Dovecot)
• Dovecot -- push plugin, push-lua
• Stalwart -- JMAP push

About JMAP (which includes push):

• marclaporte's notes on JMAP support status across mail clients