For the past two weeks an ISP has been blocking all email from our domain. The ISP insists we’ve been blacklisted but won’t tell me where. Microsoft disagrees. Instead they believe it’s a random entry in the ISP’s content filter.
Today a second ISP started blocking our email.
Now that two ISPs are blocking us, I’m more convinced we have been blacklisted. I’ve checked a bunch of blacklist tools and can only find two old references on something called clueless.org. I’ve resubmitted for evaluation. Hopefully they will be resolved.
Is there anyone out there that could help me figure things out - either by recommending blacklist tools I can check or helping me interpret my results? I started by checking the lists referenced by this article. https://sendgrid.com/blog/blacklisted-check-7-popular-blacklists-keep-reputation-intact/
I’ve dealt with black lists in the past when we hosted our own mail server and could affect the change required by the list but haven’t had to worry about that since we moved to Office 365.
I would appreciate any help anyone can provide.