Which major Mailbox Providers (MBPs) use Cloudmark for spam filtering?

Marketer from Email Geeks indicates that in Europe, the list of ISPs using cloudmark appears to include <http://Tiscali.it|Tiscali.it>, <http://Libero.it|Libero.it>, <http://TalkTalk.co.uk|TalkTalk.co.uk>, <http://Bluewin.ch|Bluewin.ch>, etc.

Email marketer from StackExchange explains that determining which specific mailbox providers use Cloudmark directly is difficult due to proprietary implementation. Suggests analysing bounce messages for possible clues.

Email marketer from Email Marketing Forum suggests checking email headers for 'X-Cloudmark-Analysis' to confirm if Cloudmark is in use by a particular provider.

Marketer from Email Geeks states that Charter, Cox, Roadrunner are showing as Cloudmarks recently from some tests run.

Email marketer from Quora responds that Comcast is known to use Cloudmark for spam filtering.

Marketer from Email Geeks shares that they are currently using Vade.

Email marketer from EmailToolTester suggests that using authentication methods such as SPF, DKIM and DMARC is crucial for deliverability, regardless of the specific spam filter used by the ISP.

Marketer from Email Geeks explains that if a domain has *.<http://cloudfilter.net|cloudfilter.net> as the MX then they are definitely using Cloudmark. Also, you can also look for our analysis strings which most customers will include in seed accounts at any of these places.

Email marketer from Reddit shares that some smaller ISPs also integrate Cloudmark through reseller agreements, making a comprehensive list difficult to obtain.

Email marketer from MailChannels Blog shares that many ISPs use a combination of commercial solutions like Cloudmark along with their in-house filtering techniques.

Email marketer from G-Lock Software Blog notes that many providers utilize combinations of different anti-spam solutions, so identifying solely Cloudmark as the only filter is often inaccurate.

Email marketer from Senderok's Blog highlights that Proofpoint, the parent company of Cloudmark, offers a comprehensive suite of email security solutions used by numerous large organizations and ISPs, but doesn't identify them directly.

Expert from Spam Resource notes that Cloudmark's effectiveness depends on its configuration and how well it's integrated with other filtering systems by the MBP.

Expert from Word to the Wise explains monitoring services may identify when an IP address is being blocked by Cloudmark, indicating that a provider using Cloudmark may be filtering messages from that IP.

Expert from Email Geeks mentions that Comcast uses Cloudmark and that Spectrum and Optimum's MXs seem to be running Synacor as a filter.

Documentation from IETF explains that SPF records are very important for your domain because they specify the mail servers allowed to send email on behalf of your domain. Filtering services can utilise this information when receiving emails from your servers.

Documentation from DKIM.org explains that DKIM is a very important email authentication method that helps prevent email spoofing - passing through email filters like Cloudmark depends on it.

Documentation from RFC-Editor Website describes standard and non-standard email header fields which helps identify possible spam filtering services used by the ISP when provided in the email headers.

Documentation from Cloudmark Website explains that Cloudmark provides anti-spam solutions to a variety of ISPs and messaging providers but does not disclose a complete list of customers for confidentiality reasons.

Documentation from Proofpoint Website details that proofpoint uses cloudmark technology to analyse email traffic and identify spam and phishing attempts, it is integrated into their larger email security suite, which is used by various mailbox providers.