In age-based retention, MailSyncer fetched the newest-N headers but only capped that window by the
retention COUNT, not the age cutoff. On a low-traffic mailbox whose newest-N span older than the
cutoff, each sync re-inserted messages the age pruner had just deleted, and the next prune deleted
them again — a churn loop of wasted DB writes + prune deletes (issue #193).
Sync now drops fetched messages older than policy.ageCutoffMillis before persisting (the same cutoff
the pruner uses), so sync and prune keep exactly the same set in both retention modes. Count/unlimited
modes have a null cutoff and are unchanged. The empty-folder wipe is keyed on the raw fetch (server
truth), so a folder holding only past-cutoff mail is left to the pruner rather than wiped.
MailPruner's KDoc now documents the sync alignment for both modes.
Closes#193
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
JMR-devandClaude Opus 4.8
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