OK people, reporting back on fetchmail container.
WORKS GREAT!
Of course I had to check the original documentation of fetchmail to make a proper for my case fetchmailrc, I made it get ALL my mailboxes and send them to proper “back-end” NS8 mailboxes and works fine AND rules work!
The only issue is that I cannot make it have a different schedule for each mailbox (in imapsync I had less important mailboxes update every 5 minutes and more important update every 3 or 1 minute), now I am forced to use a single schedule for all - but this is minor right now.
A good thing is that it locks fetchmailrc file so that passwords are not exposed (although not encoded either).
A bad thing is that I cannot make it log to a file properly (possibly my fault) - but I can see the container’s live log and I’ve seen it working.
So, great WORKAROUND and food for thought for dev team. Maybe make something of it within NS8 own GUI. It would even fix the scheduling issue, because if it was embedded in NS8, it can call fetchmail with different parameters and scheduling be done by NS8 itself (ok cron separate fetchmail tasks).
Thank’s people for giving ideas.