Why Your Email Signature Might Be Hurting Your Deliverability

Email deliverability can be the difference between success or failure of your outreach. You could be doing everything perfectly. Amazing copy, highly targeted prospects, awesome sending infrastructure—and still, your emails land in spam. Why?

One source you may not have considered: your email signature.

That little block of text (and sometimes images) at the bottom of your message may appear harmless. But to email providers, it’s a potential red flag—especially in cold outreach campaigns.

In this post, we’ll cover how your email signature might be harming your deliverability behind the scenes, mistakes to steer clear of, and how you can create a crisp, compliant, and deliverability-friendly signature that also looks professional.

Let’s dive in.

Email signature mistakes that harm deliverability

Even a well-intentioned email signature can become a liability if not designed with deliverability in mind. Signatures should look professional and informative, but design and content decisions can trigger spam filters or erode trust with email service providers.

Here are the most frequent signature blunders we see:

Overuse of links

Each link in your email increases the scrutiny from spam filters. When your signature has more than one link (your website, LinkedIn, your Instagram, and so on), it sounds the alarm. Why? Because links in an email are a signature of spam, phishing and mass marketing efforts. One to two relevant links should be enough.

Embedded or hosted images

There’s a good chance that having images (such as logos, badges, or banners) in your signature may look professional, but may also ruin your email’s deliverability. 

According to Klaviyo, spammers would often resort to images as a way to evade using spam-filter-triggering words. However, email service providers have evolved.

Email filters now look at the image-to-text ratio, and the more images you have—especially without meaningful accompanying text—the more likely your message is flagged. Also, many email clients block images by default, leaving your signature blank or broken.

HTML-heavy designs

An email signature bloated with HTML styling—custom fonts, embedded tables, inline CSS—can trigger spam filters and lead to inconsistent rendering across email clients. Excessive formatting looks like automation or templated marketing to ESPs, which lowers trust.

What this looks like:

• Multiple font types/sizes
• Colored text blocks
• Custom social media buttons in HTML tables

Overly promotional or salesy copy

Spam filters aren’t just looking at structure, either—they run checks on language. Buzzwords like “Buy Now,” “Free Trial,” or “Limited Offer,”can kill your deliverability on the spot. Your signature should be neutral, not promotional.

🔖 Related Reading: Words That Trigger Spam Filters (And How to Fix Them with a Template Checker)

How to design an email signature that helps with your deliverability

A good signature doesn’t just avoid hurting your deliverability—it can actively support it.

By keeping things simple, consistent, and optimized for email filters, your signature becomes part of a trusted sender pattern that inbox providers come to know and be familiar with over the course of time. Think of it as digital hygiene: simple, pristine, and easy for spam filters to allow.

Here’s how to create a signature that actually works for you, and not against it.

Follow the less-is-more rule

Simple is best for cold outreach signatures. You’re not writing a bio, or itemizing your entire social presence. You’re simply verifying who you are and how to reach you.

Best practices include:

• Include only your name, job title, and company name
• Steer clear of slogans, disclaimers, quotes, or awards
• Keep it to 2–4 lines total
  

Example:

Jane Doe  

Head of Partnerships | Warmy

www.warmy.io

Use text instead of images as much as possible

If your logo or photo isn’t mission-critical, skip it.Text signatures are much quicker to load, display better and get around filters much easier. Yes, email signatures are used primarily for branding and awareness—but images rarely show up as expected. Plus, they often cause more harm than good.

Here are some reminders:

• Avoid logos, especially when doing cold outreach
• Replace image-based social icons with text (e.g. “LinkedIn: /janedoe”)
• If you must use an image, host it securely and compress it

Use trusted tools 

When using an email signature builder tool, be cautious. Many online signature generators overcomplicate the HTML with inline styling, unnecessary elements, or table-based designs.

Messy code = suspicious to filters.

Warmy’s Signature Builder is a reliable, tried, and tested email signature builder designed to complement cold outreach efforts.

Align signatures across the team

Consistency builds domain trust. When every sender on your team uses the same clean signature, it shows ESPs that your messages come from a legitimate, well-managed source.It also prevents user-level mistakes like broken links or mismatched branding.

Final checklist: cold email signature best practices

Before you hit send, run through this quick checklist to make sure your signature isn’t silently hurting your deliverability.

• Less images, less mistakes. 
• Use basic fonts like Arial or Helvetica; no special styles or colors
• Keep it short at 2–4 lines max. Avoid quotes, awards, or legal disclaimers.
• Implement the same signature template across the team.
• Clean HTML (if any). Avoid messy code or styling from copy/paste or free generators
• No marketing language! Stay clear of phrases like “Free trial” or “Act now!”

How to use Warmy’s Email Signature Builder to improve your deliverability