1. Use Custom Domains Whenever Possible

Generic domains associated with free URL shorteners are more likely to be flagged due to their public availability and frequent misuse. Using a custom short domain allows you to maintain control and build a reputable sender history tied to your own brand. Custom domains increase transparency and reduce the risk of being grouped with bad actors.

2. Avoid Excessive Redirect Chains

Excessive or complex redirects can trigger red flags for security filters. Ideally, a short link should redirect once to the final destination. Long redirect chains create uncertainty for the user and for security systems, increasing the likelihood of being blocked or flagged as suspicious.

3. Ensure Your Destination URLs Are Safe and Secure

Make sure the final URLs behind your short links:

• Use HTTPS (SSL encryption)

• Do not host malware or suspicious scripts

• Are not on any known threat or spam lists

• Load quickly and do not return frequent errors (e.g., 404 or 500)

Security scanners will check not only the short URL but also the page it resolves to. A safe, reliable destination is essential.

4. Limit Short Links in Email and SMS Campaigns

Overloading your emails or messages with too many links—especially shortened ones—can increase your spam score. Keep the number of links reasonable, and avoid repeating the same short URL multiple times. Always test your messages with spam-checking tools before launching a campaign.

5. Avoid Sending to Purchased or Unverified Lists

Sending short links to email lists that have not opted in or have questionable data quality increases the likelihood of spam complaints and blacklist hits. Always use verified, permission-based contact lists and follow proper unsubscribe practices.

6. Monitor Your Domain Reputation

Use domain reputation monitoring tools to regularly check the status of your custom short domain. If your domain becomes associated with spam or flagged by DNS-based blacklists (DNSBLs), address the issue immediately by identifying the root cause and requesting delisting once resolved.

7. Implement Abuse Prevention and Rate Limiting

If your short link service allows public usage or shared access, implement rate limits, bot detection, and abuse reporting. Ensure that short links are not being automatically generated and abused by unauthorized users. Regular audits and IP monitoring can help detect and prevent suspicious activity.

8. Set Appropriate Expiration Policies

For time-sensitive campaigns, set expiration dates for short links. This ensures old or inactive links don’t lead to outdated content or error pages, which could affect your reputation over time. Redirect expired links to a safe fallback page with a friendly message, rather than letting them break.

9. Communicate Link Purpose Clearly

Where possible, include surrounding text in your emails or messages that explains what the link is for. For example:
“Click the link below to download your invoice:”
This helps spam filters and users alike understand the intent of the message and reduces suspicion around the link itself.

Conclusion

Short url are highly useful when used responsibly, but they come with the added responsibility of maintaining trust, security, and clarity. By using a custom domain, monitoring your reputation, and following best practices in link creation and distribution, you can minimize the risk of being blacklisted and ensure your communications remain effective and credible.