So an outgoing reply email message is being classified as spam by I believe MXroute filter003: part of message below to field removed.
Delivery to the following recipient failed permanently:(mailto) Technical details of permanent failure: 554 Message rejected on 2020/02/02 08:10:45 GMT, policy (220.127.116.11) ID (5E32F52A007DDF1A) - Your message looks like SPAM or has been reported as SPAM Received: from filter003.mxroute.com [18.104.22.168] (Authenticated sender: mN4UYu2MZsgR) by qrelay94.mxroute.com(ZoneMTA) with ESMTPA id 17004f39e96000f036.001 for ; Sun, 02 Feb 2020 08:10:39 +0000 X-Zone-Loop:
I checked the 3 reasons that mails might be marked as spam but this message as far as I can see does not match - not a test message, no executables that I know of and not spam - just gossip
Any ideas on how I can progress funding the cause.
Sorry to hear of the trouble, I hate when that happens. I ran through the logs and this does appear to be the recipient service rejecting it based on content. Content is a broad thing so I don’t want to imply that it’s just what you’d view as the body of the message. The headers will still be part of the content. It could be that there is a word somewhere in the message that is triggering it.
Even though their message claims it to be a content filter I still want to check for IP reputation and let you know that I did. I found that you tried twice and each try went out from different IPs. I found a bunch of accepted email by the recipient domain from the same IP range. I did find a bunch of failures too. My conclusion is that the recipient service has an excessive content filter and that people who use it may just not be able to receive all of their emails.
I started looking around to see if others experienced the same, and it looks to be common:
There were many more but those were a few examples I found. The only suggestion I would have left would be to use mail-tester.com and do your best to score a 10 out of 10 for your email with DKIM, etc. If you’ve done that, I think it’s okay to declare the end recipient to be using a mail service that is just too heavy handed.
I added DKIM to the email address and sent the message she sent to mail-tester and received a 10/10 score but still get rejected so seems BT is just heavy handed as you say in their spam protection. Thanks for the advice though.