X-Amavis-Alert: BANNED, message contains x.com

Hello,

today a mail has been banned (false positive). It says message contains 
x.com

X-Quarantine-ID: <gUr-nLm4MOSm>
X-Amavis-Alert: BANNED, message contains x.com


I couldnt find x.com in the mail body itself, but the mail had a zipfile 
as an attachment. The zip file probably contains invoices.

I grepped for x.com in the config files, but I couldnt find a rule.

grep -nri "x.com" /etc/amavis/
/etc/amavis/conf.d/20-debian_defaults:123:# [ qr'^\.(Z|gz|bz2)$'         
   => 0 ],  # allow any in Unix-compressed
/etc/amavis/conf.d/20-debian_defaults:200:     
#'[email protected]'           => -3.0,

In the journal:
Jul 16 14:55:07 mx2 amavis[578842]: (578842-12) Blocked BANNED (x.com) 
{DiscardedInbound,Quarantined}, [209.85.128.42]:58456 
[2a02:2455:17d4:d000:2d23:f49f:1017:f822] <[email protected]> -> 
<[email protected]>, quarantine: q/banned->
Jul 16 14:55:07 mx2 postfix/smtpd[582562]: proxy-accept: END-OF-MESSAGE: 
250 2.7.0 Ok, discarded, id=578842-12 - BANNED: x.com; ...

Anyone have any idea what's going wrong here?

Thomas B