I use to send out invitations to and minutes from the weekly meetings of the LibreOffice' design team. The issue is that my invitations get through but not the minutes. For example:
https://listarchives.libreoffice.org/global/design/ [libreoffice-design] Re: Agenda for the design/UX meeting 2017-Dec-13, Heiko Tietze, Wed Dec 13 20:12:02 GMT 2017
[libreoffice-design] Agenda for the design/UX meeting 2017-Dec-13, Heiko Tietze, Tue Dec 12 12:45:08 GMT 2017
but Nabble receives only the first message and not the reply
Tried this "Re:Agenda" thing since the plain "Minutes from..." hasn't been received for a while, and I thought of some weird threading with older messages. But likely it's some spam filter. Please advice me what to do.
First idea was that my signature blocks somehow, but yesterday I sent a message  without signing and it didn't arrive here. Another idea is that the issue is caused by the crossposting which leads to a couple of messages within a few seconds.
Sent my minutes to every mailinglist separately yesterday and Nabble accepted it on all channels. Meaning due to the cross-posting to three ML the message is received at Nabble within a very short period and you trigger it as spam therefore. Now looking for a solution.