Outgoing Mail with subject "Obtaining Your Experian Report" being blocked since 10-29-2018

Question

I manage a Sophos UTM-9 for a a "fix-your-credit" company which sends a lot of email to customers about their credit reports. This Sophos has been up for more than two years. Since 10-29-2018 I noted that all outbound email with subject line "Obtaining Your Experian Report" is quarantined as Spam. This is not a NEW subject line and has been used for a long time. Example ... 
 2018:10:31-14:18:05 REDACTED smtpd[13057]: SCANNER[13057]: id="1001" severity="info" sys="SecureMail" sub="smtp" name="email quarantined" srcip="REDACTED" from="REDACTED-Internal-User" to="REDACTED-External-User" subject="Obtaining Your Experian Report" queueid="1gHv49-0003Ob-5S" size="37610" reason="as" extra="" I have read through many threads in this forum and can see this is really a function of he SCANNER in the cloud and that reason="as" simply means Anti-Spam (thanks BAlfson Since I have made absolutely no changes to the Sophos in some time and since I have never had this issue until recently, I am curious what exactly is causing this. From previous posts on this subject it seems that it may be difficult to know exactly what triggered this as it is not an internal algorithm within the Sophos, itself. 
 Anyone experienced something similar in the last week or so. It is Halloween so maybe a ghost in the machine.[:D]

Kipland Iles · Answer

Thanks again @BAlfson. I did create the Exception but it's not a single sender. It's every agent in the company sending the same email template but that should be covered by *@<company.domain> . I noticed that some real Spam was still getting quarantined and marked simply as Spam and not Confirmed Spam so maybe changing that setting was not really all inclusive so I will change it back as it appears my anti-spam exception is what really fixed it (or allowed it for now). 
 Thanks for the KB article. I may pursue that but this Sophos is at a company that was just bought out and the new owners will probably replace my equipment with theirs and then it will be their problem. They like Palo Alto so the Sophos will likely be removed within the next few months (hope they give it back to me :-). 
 I did verify that their MX is not blackholed so hoping the recipients are not having issues. This customer had very stringent requirements to keep all communications behind the firewall so they use Zimbra in-house and Zimbra just relays through the Sophos SMTP Proxy. All that is changing due to the buyout and they will likely all be Exchange Cloud soon.