As a leading SaaS provider specializing in HTML email signatures for over 13 years, we’ve helped businesses troubleshoot countless issues related to email deliverability and spam filters. If your emails are ending up in spam folders, it’s rarely due to your email signature alone—but a poorly designed or misconfigured signature can contribute to spam triggers if best practices aren’t followed.
Spam filters analyze multiple factors when determining whether an email should be delivered to the inbox, flagged as spam, or blocked entirely. Excessive images, too many links, large file sizes, or improper HTML formatting in an email signature can increase the likelihood of triggering spam filters (Cisco Talos). Additionally, misconfigured DNS records like SPF, DKIM, and DMARC can also impact how email servers assess the legitimacy of your emails.
In this guide, we’ll break down the key reasons your email signature might be affecting deliverability, common spam triggers, and best practices to ensure your emails reach the inbox while maintaining a professional, polished signature.
Your Email Signature Isn’t the Direct Culprit
Most of the time, spam filters flag emails due to issues with the email's content, sender reputation, or technical configurations—not the signature. That said, certain signature design choices can raise red flags.
Common Email Signature Mistakes That Can Trigger Spam Filters
Too Many Images or Large Image Files
- Spam filters often flag emails with excessive images or emails where the ratio of text to images is too low.
- Large image files can also make your email appear suspicious and increase load times.
Solution:
- Use small, optimized images with alt text (e.g., a logo or social media icons).
- Ensure a healthy balance between text and images in your email.
Using Spammy or Broken Links
- Including links with tracking parameters or using URL shorteners like Bitly can look suspicious.
- Broken or insecure links (not HTTPS) can also cause issues.
Solution:
- Use clean, direct URLs with HTTPS.
- Avoid overly promotional CTAs like “Click here to win $$$!” in your signature links.
Excessive HTML or Poorly Written Code
- Complex or bloated HTML, especially if copied from tools like Word, can cause rendering issues and trigger spam filters.
- Incorrectly formatted or invalid HTML can also raise flags.
Solution:
- Use a dedicated email signature generator like Email Signature Rescue, which creates clean and professional HTML signatures.
- Test your signature for HTML validation errors.
Embedding Images Instead of Hosting Them
- Embedding images directly in the email signature increases the email's size and can make it look suspicious to spam filters.
Solution:
- Host images externally on a secure server and link to them in your signature.
Overloading the Signature with Too Much Content
- Signatures with long disclaimers, unnecessary quotes, or six promotional banners can overwhelm the email and reduce its professional appearance.
Solution:
- Keep your signature concise, with essential contact information, a small logo, and a simple CTA.
