pgp signature attachement flagged as encrypted attachement - mail quarantined

Question

Dear all 
 I am having quite a strange behaviour with my UTM 9 (fully up-to-date Formare 9.509-3). It started a few weeks ago (can pinpoint the exact time) that certain messages were being quarantined even though they seemed to be ok (Having a 100kB unencrypted PDF attached). I just realised that the link between those was that the messages have a .dat Attachement that contains a pgp signature. I can reproduce the problem on my system by attaching the dat file to an email and send it to me. The message gets moved to quarantine. Does anybody have the same problem or know a workaround (other than disabling the quarantine for unscannable mails / attachements)? 
 
 Typical log entry: 
 2018:05:03-10:50:33 mailgateway smtpd[13870]: SCANNER[13870]: id="1001" severity="info" sys="SecureMail" sub="smtp" name="email quarantined" srcip="xxxx.xxx.xxxx.xxxx" from="redacted@domain.com" to="redacted@domain.com" subject="test" queueid="1fE9wf-0003bi-5h" size="1776" reason="unscannable" extra="Encrypted archive" 
 Content of "Unbenannte Anlage 00016.dat" 
 -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.9 (GNU/Linux) 
 iFYEABEKAAYFAlrhkRQACgkQpuuhc59vyKvLjADfeKw/ynArkkyJpieYK+bUlRsQ ysRrJhy7LaFTFQDg1zpKLNdk/zYOwxXBWA2k+NQPZc6KzWDK2ZUHIg== =5/hS -----END PGP SIGNATURE----- 
 
 Thanks for your replies

n.o.b.o.d.y · Accepted Answer

Hello, 
 after some tests I found a work a round for me. I switched from double virus scan to single scan with Avira. Looks like the Sophos scanengine is buggy.

BAlfson · Answer

Probably a Sophos virus pattern problem. Setting scanning to just use one engine or the other should be a short-term necessity. 
 Cheers - Bob

sachingurung · Answer

Hi, 
 This issue is investigated under the reference ID: NUTM-9853. The development team is working on a fix but we do not have an ETA yet. 
 Thanks,

nca · Answer

Dear All 
 The issue is resolved with the current version 9.6 of our UTM. 
 
 Before updating to 9.6 please make sure you re-enable dual-scanning to ensure that both engines get updated.

pgp signature attachement flagged as encrypted attachement -> mail quarantined