Hi,
I run two very low traffic Mailman lists on my Linode. This morning one of them got an Email, and that's when I found out thanks to Comcast that my IP is on Cloudmark's blacklist. Naturally I've sent in a reset request using the form linked from the Comcast error message, and am still waiting to be removed. A few days ago I sent to a Comcast customer with no problem.
I've resolved the problem sending to Comcast by enabling my server to send using IPv6. This required me to have Linode allocate me my own /64 since my default IPv6 address was in a /64 blocked by Spamhaus XBL/CSS lists.
Does anyone know if Cloudmark blocks entire IP ranges or just individual addresses? I don't know why my IP is on Cloudmark's list, as most of the Email I send is personal in nature, to people I have corresponded with for years. I've used multiple RBL check tools, and everything has come back negative, except that my entire subnet is on Spamgrouper.to (checked by running a check on a neighboring IP). I have SPF, DKIM, and DMARC set up.
I'm getting really tired of these unexplained blacklistings. Does anyone know of any reliable outgoing Email service providers? Ideally I want to continue to handle my own incoming Email because I don't want someone else's spam blocking software deciding what Emails I receive.
Thanks,
Jayson