-={ 2021-04-12 22:17:06.607549879+00:00 }=-

Hey August!

 AA> My system has both of these

Perfect!  That confirms that the address is indeed part of the dupe checking routine.

 AA> [1] == MID: 1:153/7001 8QIOgQad
 AA> [2] == MID: 1:153/7001.2989 8QIOgQad

That is what I see here.  Also there is no doubt they are completely different MSGs, from two different systems.  Right?  Also it appears from this angle that your idea for the random serial number is indeed compliant with fts-0009.001 despite objections anyone might have about the methodolgy.

 AA> Perhaps you need to keep the "address" part the same for a valid
 AA> test.

This was a perfectly valid test.  If you actually need to see if it will pick up on a duped MSGID we could try that as well.  I'll follow up this reply of a totally new MSG with the "1:153/7001 8QIOgQad" address serial number.  Don't touch that dial!

Life is good,
Maurice

... Wa ¨‘re ¨eode ¨e h‘f¨ ‘l¨eodigne cyng.
    Woe will come to the nation which has a foreign king.
--- GNU bash, version 5.1.4(1)-release (x86_64-motorshed-linux-gnu)