Since February 2024, Google’s email sender guidelines require senders of 5,000+ daily messages to Gmail to authenticate outgoing email. SPF and DKIM are mandatory, plus DMARC alignment. Miss the alignment requirement and your messages get rate-limited or rejected.

Here’s the problem: if you’re sending from your domain but tracking clicks through a shared domain, you’re breaking that alignment every time.

Sure, you could skip tracking altogether. But then you’re flying blind on opens and clicks.

In this guide, I’ll show you exactly how to set up a custom tracking domain in about a minute, and why it protects your deliverability.

A tracking domain is a URL used in analytics to track email opens and link clicks in your outreach campaigns. Its job is to collect these data points so you can improve your campaigns accordingly.

Your sending domain (the “From” address) is where your email appears to originate. Your tracking domain is the URL behind open pixels and click tracking. When these don’t match, inbox providers see a mismatch that can trigger spam filtering.

When you’re sending cold emails, you want to know how many people opened or clicked. By analyzing these metrics, you can identify which campaigns are working and which aren’t.

To show these stats, email automation tools insert tracking pixels and change URLs in their system. For example, they add a small 1×1 pixel that triggers every time an email gets opened.

Most emails in your inbox have that pixel. You can check it by opening “Show original” mode in Gmail:

Find the “img” tag with the parameter height=“1” width=“1”. It’s usually at the bottom of the script:

All of this affects your email deliverability and whether your prospects actually see your emails.

Tracking pixels affect your deliverability in two ways, putting you at serious spam risk:

Say your domain is donuts.com and you use lemlist as your cold email tool. According to Google’s email sender guidelines, senders of 5,000+ daily messages must authenticate outgoing email. The From: domain must align with either SPF or DKIM organizational domains.

When your tracking domain doesn’t match your sending domain, inbox providers see a mismatch. That mismatch can trigger spam filters.

Your email deliverability is also affected by other senders who use default tracking. Email automation tools have thousands of users grouped across the same domains.

To simplify: say 10 users are divided into groups of 2 across five domains. You and I end up sharing a domain. But imagine I’m a spammer who overuses the tool.

Google starts associating every email I send with spam, affecting the reputation of my tracking domain. My tracking domain is also your domain, so you suffer too.

The best email automation tools control these things and don’t let people become spammers. For example, lemlist has a rigorous way of isolating spammers, while our sending algorithm doesn’t allow spammers to overuse the tool and send blasts.

Still, you should do yourself this favor. Customize tracking links and pixels by setting up your own custom tracking domain.

Put it this way: if you’re earning enough money to live on your own, why have a roommate?

On top of that, if you customize tracking links and pixels, it adds to your sender score and improves deliverability.

Log into your lemlist account.

From the home dashboard, go to Account Settings:

If you work alone or as part of a team where all members have the same domain, set up your CTD from Team Settings → Team configuration:

If your teammates have different domains, each user will have to create a CTD from the User section.

Enter your domain (the domain of the email address you previously linked with your lemlist account) and click Check:

lemlist will automatically generate the info you need to complete your Custom Tracking Domain setup:

The “Host” name can vary from user to user. You may end up with “trail” or “route” or “lemtrail” according to their availability.

Keep these 3 values and you’re ready for the next step.

To create a subdomain, go to your domain provider and edit your domain’s DNS (Domain Name Service) records. You may need administrator access. If you don’t know how to do it, the easiest way is to ask your dev team for help.

Once you have access to your domain provider:

Each domain provider has its own interface. You may not have the exact same field names as below. We’ll cover the most common ones.

TYPE field: Select “CNAME”

NAME or HOST field: Refer to the name lemlist generated (“trail”, “route”, or “lemtrail”)

HOSTNAME or VALUE or POINTS TO field: Type “custom.lemlist.com.” (leave the final dot if accepted; if not, remove it)

If you need a tutorial for a specific domain provider, here are some our lemlist users recommend:

Click “Setup my tracking domain”:

lemlist will check your DNS records and make sure everything looks good.

It takes up to 48 hours before your DNS record gets distributed around the internet. You can also check with your host support if they see issues in their backend.

Once you’ve finished the setup, double-check that everything works:

If yes, you’re good to go.

If not, there’s an issue in your configuration. We advise you to repeat the setup with your dev team following our tutorials or the video below.

Note: You can’t use the same CTD in separate teams for security reasons. If not set under the “Team” section (used by the whole team), you can’t set the same CTD under the “User” section.

To create multiple CNAMEs for multiple teams: you probably created your current one using the subdomain “trail” to make your CTD look like trail.yourdomain.com. Follow the CNAME creation process again, but use another subdomain like “lemtrail” or “route”.

You can also set up a sending domain in lemlist with SPF and DKIM configured automatically. Once you’re sending, monitor your domain health with inbox-placement testing and real-time alerts.

A CTD is a subdomain you own (like track.yourcompany.com) that handles open and click tracking for your emails. It replaces the shared tracking URL your email tool provides by default, giving you full control over domain reputation.

Your sending domain is the domain in your “From” address (yourname@company.com). Your tracking domain is the URL behind tracking pixels and links. When these two don’t align, inbox providers can flag your messages as suspicious.

According to Cloudflare, DNS changes typically take a few minutes to 48 hours to propagate globally. Most setups are active within a few hours. You can test by visiting your subdomain in a browser.

Tracking opens and clicks is a standard practice in cold email, and most outreach tools do it by default. The part that matters is how you handle it. Under the FTC’s CAN-SPAM rules, you must honor opt-out requests within 10 business days and clearly identify commercial messages. The GDPR transparency principle requires personal data be processed lawfully and transparently. Keep your tracking tied to legitimate business outreach and give people an easy way to unsubscribe.

Recipients who hover over links or inspect email source code will see your custom subdomain (track.yourcompany.com) instead of a third-party domain. This looks more professional and builds trust.

Basic familiarity with DNS settings helps, but the process is straightforward. If you have admin access to your domain provider, you can complete setup in about a minute. If not, your dev team or IT admin can handle it quickly.

Setting up a CTD takes a few minutes, but it protects your sender reputation for every campaign you run. You avoid shared-domain risk and align your tracking with your sender identity.

If you want to take deliverability further, here are a few related guides:

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