It looks like the problem was caused by something in the way MR sends/sent mail.
Today I received two notifications
sent to my old email address. One was a notification triggered by shalym's post on 29/7/2016. It was sent to the email address which was current at that time but not the one current today.
Examining the SMTP headers for the email and comparing them with later notifications it appears that the "delayed" ones came via a8-192.smtp-out.amazonses.com (54.240.8.192) whereas the ones sent to my "new" email address come via postfach.slogh.com ([138.201.180.57]:56154). The only timestamps in the "delayed" header are for 1 August 2016.
So it seems MR initiated the emails on 28 and 29 July (based on the content of the emails and a reference to the actual threads) but these replies then "got stuck" in the email transport system at amazonses.com finally making it out today.
This looks like a similar problem to that reported in
https://www.mobileread.com/forums/sho...d.php?t=269877 back in January.
BobC