Spotted this in the maillog and then got a duplicate of two emails. Restarted dovecot and haven't seen it again:
service dovecot stop
killall -9 dovecot
service dovecot start
Oct 22 14:23:15 admin dovecot: POP3(username): mbox sync: Expunged message reappeared in mailbox mbox (UID 81 < 13499, seq=2, idx_msgs=0)
Oct 22 14:23:17 admin dovecot: POP3(username): mbox sync: UID inserted in the middle of mailbox mbox (13499 > 81, seq=2, idx_msgs=1)
Oct 22 14:46:26 admin dovecot: POP3(username): mbox sync: Expunged message reappeared in mailbox mbox (UID 81 < 13501, seq=2, idx_msgs=0)
Oct 22 14:46:28 admin dovecot: POP3(username): mbox sync: UID inserted in the middle of mailbox mbox (13501 > 81, seq=2, idx_msgs=2)
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Dan Kriwitsky
For Discount Hotel Reservations call 800-611-7450