v91

What's Changed

This release addresses the v91 (ESR) Thunderbird stable branch.

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Due to upstream sections "namespace" changes, mail-related preferences sections have been shifted from 6000 / 6100 / 6200 / 6300 to 9100 / 9200 / 9300 / 9400.
You are advised to reinstall from scratch the template and append your preferences overrides on top of it.
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Breaking

• Move mail-related preferences sections from 6XXX to 9XXX
• Disable very buggy mail.password_protect_local_cache preference
• Show a prompt when opening a link in external applications (hardening)

Added

• Apply (upstream) Arkenfox v78..v91 upstream migration
• mail.phishing.detection.* preferences
• security.osclientcerts.autoload preference
• mail.biff.show_badge new preference (TB >= v91.0.2)

Changed

• [SETTING] tags global cleanup
• Enforce mail.phishing.detection.* preferences
• Enable mailnews.sendformat.auto_downgrade preference
• Higher mail.compose.big_attachments.threshold_kb to 9220KB
• Hide sensitive information from chat desktop notifications (when enabled)

Removed

• Autocrypt and Enigmail addons related preferences
• permissions.default.* preferences (missing from TB)
• mail.cloud_files.inserted_urls.footer.link dropped preference
• toolkit.telemetry.prompted (apparently dropped) preference