Instant new mail notifications in Thunderbird Android are implemented using IMAP IDLE connections, which drain the phone battery and consequently require the user to opt-in by folder. This is a costly compromise, requiring user savvy, the opt-in UI, AND the battery drain from each IDLE connection.
Instead, Thunderbird Android should preemptively implement the client-side portion of its own IMAP extension, like the iPhone Mail app does with XAPPLEPUSHSERVICE. This will stimulate demand for server-side implementations. Forwardemail.net, for example, went to the trouble of reverse-engineering the XAPPLEPUSHSERVICE client calls and implementing the server side in their IMAP servers, because it gives their mail services "native"-like performance on the iPhone. Gmail servers don't implement IMAP at all and Google has no incentive to encourage Android users to use any other email service. As the de facto standard FOSS Android mail client, Thunderbird Android should go ahead with its own extension, and plan to phase out the awkward use of IDLE.
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