Ok after some fixing here and there on the server I managed to discover that our spam/ham training was not working, because the spam/ham account where on a server where mailbox service was disabled.
I run a multiplatform system, and the pool server was too "large", including an mta server... well... I fixed it.

I created 2 new accounts for spam and ham, and changed the server configuration in order to point there.

Evrything was working fine until I runned zmtrainsa... the system was telling me there where only 3 mail to eat in the spam mailbox. I've checked out the mailbox, and i discovered that all the spamtraining mail went.. into the Junk folder.

So now I'm guessing how much "special" those 2 special accounts really are. Any way to disable filtering on those accounts, or regenerate 2 "correct" spam/ham mailboxes ?

Thanks in advance for all help.