Amavis 0.3.12 seems to remove foreign added
"X-Virus-Scanned" lines, which can lead to problems
if the foreign software created multiline-comment.
An example for this is clamav-milter. As a consequence,
all but the first line of the clamav-milter X-Virus-Scanned
lines are appended to the subject of the message!
As a quick workaround, I changed line 240 to
$X_HEADER_TAG = "X-Amavis-Virus-Scanned";