We have a lot of problems with emails with manipulated Received-Entries.
There are emails that have the first Received-Entry like this:
Received: from ...somewhere... by urz.uni-magdeburg.de
Such lines don't come from our servers... never ....
"urz.uni-magdeburg.de" is the virtual email domain from our compute
centre ( MX to our relay server, which had received
that email).....but that isn't true . Our real receiving-entry I can
found still with the last received-entry:
Received: from ...somewhere...by mail.uni-magdeburg.de
By debugging the spam assassin (if it reads an email with that received
entries) I found lines, that tell us
... it's good... the first "by" is near the last "by"....("by" from a
received-entry)
with the result: ... -2.6 to the SPAM-Score... the email will be
accounted better as it is ....