I have seen the same email processed multiple times. For example:
$ grep 'Received Message Date: Tue, 12 Mar 2019 03:51:16' 2019-03-[12]*\ Events.txt
2019-03-11 Events.txt:2019-03-11 23:51:24.624 Better Email Pittstown IMAP: Received Message Date: Tue, 12 Mar 2019 03:51:16 +0000 (UTC)
2019-03-12 Events.txt:2019-03-12 23:47:26.980 Better Email Pittstown IMAP: Received Message Date: Tue, 12 Mar 2019 03:51:16 +0000 (UTC)
2019-03-13 Events.txt:2019-03-13 00:29:28.339 Better Email Pittstown IMAP: Received Message Date: Tue, 12 Mar 2019 03:51:16 +0000 (UTC)
2019-03-13 Events.txt:2019-03-13 00:40:14.244 Better Email Pittstown IMAP: Received Message Date: Tue, 12 Mar 2019 03:51:16 +0000 (UTC)
Thanks for all of your great plug-ins.