Mailbox providers use sophisticated machine learning filters to examine certain "clusters" of data points, or elements, like email content, IP address, subject line, etc., and will record if any of the combinations of these elements result in low engagement and spam complaints.

Based on the elements that cause most spam complaints, certain "fingerprints" are recorded and they will be used to compare the fingerprints of other users' emails and decide whether they are spam or not.

Let's say one of your sending domains has been added to the blocklist. Instead of changing it, look at your cold emails on a larger scale, and all their elements to find what needs to be fixed to leave a more positive fingerprint for the cluster of sending elements you are using.

If you are having deliverability issues, just a new domain will never fix that problem. Instead, look for reasons your recipients would feel that what they are receiving is not what they find valuable and adjust your copy accordingly.

If recipients simply aren’t engaging with your content, then you will likely want to spend effort on crafting more engaging content, offers, and subject lines.

Senders don’t necessarily run into problems simply because of a “bad” IP or domain or sending infrastructure. Senders can also run into delivery or inboxing issues because their email sending patterns are generating signals that match a fingerprint of unwanted mail in the mailbox provider’s eyes.

A simple content reputation cluster example.
Imagine an email campaign that generates a lot of spam complaints. Inbox providers will examine the following elements:

The inbox provider will not only look at each element individually but also if any combination of two or more of those elements correlates to low engagement and spam complaints. The more elements they consistently see generating these results as a “cluster,” the more that cluster builds its own reputation fingerprint. This allows mailbox providers to be much more accurate in their filtering than in times past.

Low open and reply rates are a clear indication to ISPs that your recipients are not interested in your offer or your content in terms of email deliverability.

The success of future campaigns is affected by this lack of engagement, and it may even result in the blocking of your campaigns. You are damaging your deliverability further by continuing to send the same email copy or to the same audience who doesn't find it relevant.

How recipients react to the email you send them determines the reputation of all of the sending elements you are using. Focus your efforts on pleasing your audience and structuring your email campaign so that you control those clusters and more clearly demonstrate that recipients want your emails. Also, make sure to regularly switch out the contents of your cold email and come up with fresh copy, especially if you're sending high volumes.

Our copywriting guide can help you craft engaging emails.

Read more about the topic of fingerprinting on https://sendgrid.com/blog/email-reputation-clusters-and-fingerprinting/