In a world where email marketers compete for open rates, click-through rates, and conversions, the email signature may easily be overlooked. Or it may even be a last-minute addition.
However, did you know it could actually be the difference between your email landing in the inbox or getting lost in the spam folder?
The battle for the inbox
Does your signature help you establish trust? Does it make your email look legitimate? Or, does it raise red flags that send your message straight to the spam folder?
Also, what is it about certain email signatures that can tip the scales in your favor? What makes one signature type more effective than another?
These are the questions that the Warmy Research Team seeks to answer in the latest report.
The showdown: How signatures affect deliverability across ESPs
- This experiment tested six signatures and one baseline across OpenSRS, Microsoft365, and G Suite.
- All templates were in plain text format and each signature contained the name of the recipient and the sender. The baseline template had no signature.
Here is a quick look at what each email signature template looks like:
Ready to see how your email signature stacks up in the battle for the inbox? Let’s dive in!
The key players: What goes into an email signature?
In the showdown of email signatures, every element of your signature plays a vital role. Let’s break down the essential components of an email signature and explore their impact on inbox placement.
- Contact information: The sender’s email address, phone number, and physical address must ideally be visible in the email signature. These elements build credibility and trust.
- Company details: Your company name and other official links such as website or social media profiles can contribute to branding and make your email appear even more legitimate.
Signature Showdown: Testing signatures across top email providers
Gmail, MS365, and OpenSRS all have unique algorithms and own sets of rules for how they evaluate emails
In this round, we’ll take a look at how email signatures affect deliverability across these top providers and which signature strategies help—or hurt—your chances of landing in the inbox.
Round 1: OpenSRS: The baseline template as the surprise victor
- The baseline template, which contains no signature, performed better than most custom signature configurations with a deliverability rate of 63.46%.
- Of the six signature templates, Signature 1 had the lowest deliverability rate at 40.33%. Compared to the other templates, Signature 1 was the most cluttered and had the most information.
- Summary of findings:
- Using 3rd signature will decrease your delivery by 0.26%
- Using 6th signature will decrease your delivery by 0.60%
- Using 5th signature will decrease your delivery by 1.20%
- Using 2nd signature will decrease your delivery by 1.40%
- Using 4th signature will decrease your delivery by 3.46%
- Using 1st signature will decrease your delivery by 23.13%
Key takeaway: In OpenSRS, less is more. The baseline template performed the best, and complex signatures with multiple details, especially Signature 1, significantly harmed deliverability.
Round 2: GSuite: When subtle moves get the big wins
- The baseline performance for G Suite emails is 62.80%. However, the impact of signatures varies slightly more compared to OpenSRS and MS365.
- For G Suite, Signature 5 and Signature 6 perform slightly better than the baseline at 64% and 63.66% respectively, while the Signature 1 significantly reduces delivery rate at 42.1%.
- Signature 5 and Signature 6 had the least details—just the sender name and one mode of contact.
- Summary of findings:
- Using 5th signature will increase your delivery by 1.20%
- Using 6th signature will increase your delivery by 0.86%
- Using 2nd signature will decrease your delivery by 1.94%
- Using 3rd signature will decrease your delivery by 2.80%
- Using 4th signature will decrease your delivery by 3.34%
- Using 1st signature will decrease your delivery by 20.74%
Key takeaway: For G Suite, signatures with minimal contact information (such as Signature 5) provide the best results. Overloading your signature with information reduces deliverability, especially with Signature #1.
Round 3: MS365: Small tweaks make the difference
- MS365 has a baseline deliverability rate of 61%. However, small tweaks in the signature can slightly improve or reduce this rate.
- Signature 1 (company name, phone number, social links, email, physical address) generated a significant 16.70% decrease in deliverability. It seems that the more detailed the signature, the worse it performs in MS365’s spam filters. Signature 5 had the highest deliverability rate at 62.1%.
- Summary of findings:
- Using 5th signature will increase your delivery by 1.13%
- Using 6th signature will increase your delivery by 1.00%
- Using 2nd signature will increase your delivery by 0.26%
- Using 4th signature will increase your delivery by 0.26%
- Using 3rd signature will increase your delivery by 0.20%
- Using 1st signature will decrease your delivery by 16.70%
Key takeaway: In MS365, simple signatures—such as Signature #6 (contact email only)—offer the most significant performance boost. Complex signatures (like Signature #1) are flagged the most, harming deliverability.
Signature Showdown recap: Which one works best?
Throughout our research, we compared various signature templates, ranging from minimal (just an email address) to more complex templates that include company names, phone numbers, and social media links.
Each signature was tested across Open SRS, G Suite, and MS365—giving us valuable insights into what works and what doesn’t.
While the baseline template (no signature) emerged as the surprise victor in most cases, signatures that were minimal in detail performed consistently better across the board.
However, as we added different elements to the signature, performance began to vary.
OpenSRS
- Baseline template: With a deliverability rate of 63.46%, it outperformed every custom signature configuration.
- Signature 1 (most complex): A 23.13% decrease in deliverability
G Suite
- Signature 5 performed best at 64%.
- Signature 1 had a 20.74% drop, clearly showing that too much detail is detrimental.
MS365
- Signature 5 had the highest deliverability at 62.1%.
- Signature 1 had a massive 16.70% decrease, making it the worst performer.
Based on our findings, here’s the winning strategy for creating the perfect signature:
- Stick to the basics: Keep your signature simple—just the essentials like your contact email and phone number. This will help avoid triggering spam filters.
- Branding is okay, but keep it light: If you want to add branding, include your company name and website link. But avoid excessive details, especially social media links and physical addresses.
- Test your signatures: Every email provider has its own quirks. What works for Gmail might not work for MS365. Don’t be afraid to experiment with your signature and test which works best for your audience.
How Warmy’s Signature Builder can help you craft email signatures that work for you
Creating the perfect email signature can be tricky. Fortunately, Warmy’s Signature Builder is here to help you navigate this challenge.
It provides an easy and effective way to craft professional, high-performance email signatures tailored to your needs. It drastically simplifies the process of designing and optimizing your email signature by offering tested and proven templates with customization options. You don’t need to be a designer or a deliverability expert to create a signature that works.
Sign off your emails with a bang
With Warmy’s Signature Builder, you don’t have to guess or worry about how your email signature is affecting your deliverability. You won’t only be able to end your emails with impact, you’ll also be experiencing higher inbox placement.
Download the full report here for the full insights on email signatures and their impact on your deliverability.
