Stalwart 0.14.x does not increment HIGHESTMODSEQ when new mail arrives
via SMTP delivery, so the incremental sync's CONDSTORE fast-path saw
serverModSeq == storedModSeq and returned early — silently skipping
UID SEARCH and missing any newly received messages.
Fix: remove the early-return fast-path. Incremental sync now always
runs UID SEARCH UID ${lastUid+1}:* to discover new messages. CONDSTORE
is still used for the flag-refresh gate (only runs when modseq changed),
which is its correct, narrower role.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
