The mailing list for listmasters using Sympa

[Riccardo Veraldi <address@concealed>]

Hello,
SYMPA 6.1.7
there are some messages arriving to sympa which are not tagged a spam, 
but they are moved anyway into bad/
directory.

I cannot understand why they are moved there, and sympa gives no reason 
for it in the log file.
What i noticed is that these messages are coming from other remote 
mailing lists which write message to mailing lists on my server.
How can I avoid this valid message to be put into bad/ and being 
processed as normal messages ?

thank you

Rick