How Link Reputation Affects Cold Email Deliverability
Links in cold email are scanned by spam filters. A single bad link can cause spam placement even when everything else is configured correctly.
Most cold email operators focus on domain reputation and authentication when diagnosing spam placement. Links are often overlooked — but a single URL in your email that's on a reputation list, resolves to a suspicious domain, or is flagged by a security scanner can cause spam placement regardless of everything else being correct.
How link reputation filtering works
Spam filters check every link in your email against multiple reputation databases. If any link resolves to a domain that's on a URL reputation list (like SURBL, URIBL, or Google Safe Browsing), the email is flagged. This check happens at the receiving server, so it's invisible to your ESP.
The most common scenario: a cold email operator embeds a link to their client's website — and the client's website domain has been on a spam reputation list at some point. The operator doesn't know this, campaigns run for weeks in spam, and the issue is never diagnosed correctly.
What to check
Your tracking domain
The tracking domain is the most common culprit. Click tracking wraps your links in a redirect through your tracking domain. If that domain is on a reputation list, every tracked link in every email has a reputation problem. Run the tracking domain checker.
Destination URLs
The URL you link to — your landing page, your client's website, your calendar booking link — can also be on reputation lists. Run the destination domain through the link reputation checker.
Shortened URLs
Shortened URLs (bit.ly, tinyurl, custom short links) are aggressively filtered by spam filters because they hide the final destination. Avoid URL shorteners in cold email entirely.
Multiple links
Each link in your email is an additional surface for reputation scanning. Cold email should have a maximum of one link — ideally zero or just a calendar link. Every additional link increases filtering risk.
Using the link reputation checker
The link checker extracts all URLs from your email content and checks each one against reputation databases. Paste your email and get a report on which links are clean and which have issues.
Best practices for links in cold email
- Maximum one link per email — ideally your calendar link
- Never use URL shorteners
- Use a dedicated tracking domain separate from all sending domains
- Check your tracking domain monthly
- Check destination domains when onboarding new clients
- Plain text links are safer than hyperlinked text (fewer spam signals)
What to do if you find a problem
If your tracking domain is on a reputation list, you may need to set up a new tracking domain. If a destination URL is on a list, use a different URL or remove the link entirely for the affected campaigns. If a client's domain is the issue, the client may need to address their website's reputation independently — and you may need to avoid linking to it in campaigns until it's resolved.
Run the checks first
Before replacing anything, run a free inbox placement test. You might find the issue is DNS, not the domain — and save yourself a week of unnecessary work.