Permanently classified as spam with huge score, why?

[annc]

Hi everyone,


One of our customer has a problem with blocking email with this error:

"2017-03-19 19:55:16 1cpfyt-00036z-PK H=sender-of-o52.zoho.com [135.84.80.217] X=TLSv1.2:ECDHE-RSA-AES256-SHA384:256 CV=no F=<[email protected]> rejected after DATA: Your message to <---CUT---l> was classified as SPAM. Please add more content, cut down on HTML links, use fewer naughty words etc. Also, ask your IT dept to make sure your mailserver has REVERSEDNS, SPF and is not on any black lists. Your score: 160"

As you see, this domain uses zoho.com mail services.
Problem exist even when [email protected] sends empty email.

I checked SPF and blacklist for this domain via https://mxtoolbox.com. Everything looks fine.
I'm using latest ESF with default config.

Any ideas what could be wrong?

 

[Richard G]

Check this:
https://intodns.com/ac-admin.pl

Looks like one of your nameservers is not responding:
ERROR: One or more of your nameservers did not respond:
The ones that did not respond are:
31.186.85.134
(» ns2.dqserwis.pl. not responding).
This is probably not causing this issue, but you might like to fix this or have this fixed.

Is this with all mail or with certain mail? Because the error says the cause might be too less content (like empty mail) or too many html links and/or naughty words. The receicing party might have a strict filter.