I found some strange log recectly,my version is: Version: 7.3-3,the log is as below:
Apr 18 19:00:08 postfix pmgproxy[1125188]: detected empty handle
Apr 18 19:00:13 postfix pmgproxy[1125188]: detected empty handle
Apr 18 19:00:18 postfix pmgproxy[1125188]: detected empty handle
Apr 18 19:00:23 postfix pmgproxy[1125188]: detected empty handle
Apr 18 19:00:28 postfix pmgproxy[1125188]: detected empty handle
Apr 18 19:00:32 postfix pmg-smtp-filter[1133794]: starting database maintenance
Apr 18 19:00:32 postfix pmg-smtp-filter[1133794]: end database maintenance (4 ms)
Apr 18 19:00:33 postfix pmgproxy[1125188]: detected empty handle
Apr 18 19:00:38 postfix pmgproxy[1125188]: detected empty handle
Apr 18 19:00:43 postfix pmgproxy[1125188]: detected empty handle
Apr 18 19:00:48 postfix pmgproxy[1125188]: detected empty handle
Apr 18 19:00:53 postfix pmgproxy[1125188]: detected empty handle
Apr 18 19:00:59 postfix pmgproxy[1125188]: detected empty handle
Apr 18 19:01:04 postfix pmgproxy[1125188]: detected empty handle
Apr 18 19:01:09 postfix pmgproxy[1125188]: detected empty handle
Apr 18 19:01:14 postfix pmgproxy[1125188]: detected empty handle
Apr 18 19:01:19 postfix pmgproxy[1125188]: detected empty handle
Apr 18 19:01:24 postfix pmgproxy[1125188]: detected empty handle
Apr 18 19:01:29 postfix pmgproxy[1125188]: detected empty handle
Apr 18 19:01:34 postfix pmgproxy[1125188]: detected empty handle
Apr 18 19:01:36 postfix pmgmirror[881470]: starting cluster synchronization
Apr 18 19:01:36 postfix pmgmirror[881470]: cluster synchronization finished (0 errors, 0.00 seconds (files 0.00, database 0.00, config 0.00))
Apr 18 19:01:39 postfix pmgproxy[1125188]: detected empty handle
Apr 18 19:01:44 postfix pmgproxy[1125188]: detected empty handle
Apr 18 19:01:49 postfix pmgproxy[1125188]: detected empty handle
Apr 18 19:01:54 postfix pmgproxy[1125188]: detected empty handle
Apr 18 19:01:59 postfix pmgproxy[1125188]: detected empty handle
Apr 18 19:02:04 postfix pmgproxy[1125188]: detected empty handle
Apr 18 19:02:09 postfix pmgproxy[1125188]: detected empty handle
Apr 18 19:02:12 postfix pmgpolicy[881454]: starting policy database maintenance (greylist, rbl)
Apr 18 19:02:12 postfix pmgpolicy[881454]: end policy database maintenance (12 ms, 1 ms)
Apr 18 19:02:14 postfix pmgproxy[1125188]: detected empty handle
Apr 18 19:02:19 postfix pmgproxy[1125188]: detected empty handle
Apr 18 19:02:24 postfix pmgproxy[1125188]: detected empty handle
Apr 18 19:02:29 postfix pmgproxy[1125188]: detected empty handle
Apr 18 19:00:08 postfix pmgproxy[1125188]: detected empty handle
Apr 18 19:00:13 postfix pmgproxy[1125188]: detected empty handle
Apr 18 19:00:18 postfix pmgproxy[1125188]: detected empty handle
Apr 18 19:00:23 postfix pmgproxy[1125188]: detected empty handle
Apr 18 19:00:28 postfix pmgproxy[1125188]: detected empty handle
Apr 18 19:00:32 postfix pmg-smtp-filter[1133794]: starting database maintenance
Apr 18 19:00:32 postfix pmg-smtp-filter[1133794]: end database maintenance (4 ms)
Apr 18 19:00:33 postfix pmgproxy[1125188]: detected empty handle
Apr 18 19:00:38 postfix pmgproxy[1125188]: detected empty handle
Apr 18 19:00:43 postfix pmgproxy[1125188]: detected empty handle
Apr 18 19:00:48 postfix pmgproxy[1125188]: detected empty handle
Apr 18 19:00:53 postfix pmgproxy[1125188]: detected empty handle
Apr 18 19:00:59 postfix pmgproxy[1125188]: detected empty handle
Apr 18 19:01:04 postfix pmgproxy[1125188]: detected empty handle
Apr 18 19:01:09 postfix pmgproxy[1125188]: detected empty handle
Apr 18 19:01:14 postfix pmgproxy[1125188]: detected empty handle
Apr 18 19:01:19 postfix pmgproxy[1125188]: detected empty handle
Apr 18 19:01:24 postfix pmgproxy[1125188]: detected empty handle
Apr 18 19:01:29 postfix pmgproxy[1125188]: detected empty handle
Apr 18 19:01:34 postfix pmgproxy[1125188]: detected empty handle
Apr 18 19:01:36 postfix pmgmirror[881470]: starting cluster synchronization
Apr 18 19:01:36 postfix pmgmirror[881470]: cluster synchronization finished (0 errors, 0.00 seconds (files 0.00, database 0.00, config 0.00))
Apr 18 19:01:39 postfix pmgproxy[1125188]: detected empty handle
Apr 18 19:01:44 postfix pmgproxy[1125188]: detected empty handle
Apr 18 19:01:49 postfix pmgproxy[1125188]: detected empty handle
Apr 18 19:01:54 postfix pmgproxy[1125188]: detected empty handle
Apr 18 19:01:59 postfix pmgproxy[1125188]: detected empty handle
Apr 18 19:02:04 postfix pmgproxy[1125188]: detected empty handle
Apr 18 19:02:09 postfix pmgproxy[1125188]: detected empty handle
Apr 18 19:02:12 postfix pmgpolicy[881454]: starting policy database maintenance (greylist, rbl)
Apr 18 19:02:12 postfix pmgpolicy[881454]: end policy database maintenance (12 ms, 1 ms)
Apr 18 19:02:14 postfix pmgproxy[1125188]: detected empty handle
Apr 18 19:02:19 postfix pmgproxy[1125188]: detected empty handle
Apr 18 19:02:24 postfix pmgproxy[1125188]: detected empty handle
Apr 18 19:02:29 postfix pmgproxy[1125188]: detected empty handle