Can I perform IP warming with single image emails?
Matthew Whittaker
Co-founder & CTO, Suped
Published 29 May 2025
Updated 15 Aug 2025
6 min read
When approaching IP warming, a common question arises about the suitability of using emails that consist solely of a single image. The short answer is yes, you *can* send single image emails during IP warming, but it is generally not recommended. While the primary goal of IP warming is to gradually increase email volume and establish sending patterns, the content of your emails plays a crucial role in building a positive sender reputation with mailbox providers (ISPs).
The objective is to demonstrate to ISPs that your email stream is legitimate and desired by recipients. Sending emails that are primarily or solely image-based can introduce significant challenges to this process. ISPs, like Google and Yahoo, assess not just the volume but also the content and recipient engagement to determine your sender reputation.
Why content matters for IP warming
IP warming (also known as a blocklist or blacklist warm-up) is the systematic process of gradually increasing the volume of email sent from a new or previously unused dedicated IP address. This helps to establish a positive sending reputation with internet service providers (ISPs). Without proper warming, a sudden influx of emails from a new IP can be flagged as suspicious or spam, leading to emails being throttled, delayed, or outright blocked.
The goal is to show ISPs that you are a legitimate sender with engaged recipients. This involves more than just volume; it's also about content quality and how recipients interact with your emails. Engagement metrics like opens, clicks, and replies signal to ISPs that your emails are valued, whereas bounces, spam complaints, and unsubscribes negatively impact your reputation.
While the immediate impulse might be to use existing, easy-to-create content like single-image emails for warming, it's crucial to consider the long-term implications for your sender reputation and overall email deliverability. Your warm-up period sets the tone for your IP's reputation.
Risks of warming with single image emails
Warming an IP address with emails composed solely of a single image can significantly undermine your efforts. This practice often triggers spam filters, leading to poor inbox placement. It also reduces user engagement, as images may not load by default, making calls to action invisible.
The challenges of single image emails for deliverability
Single-image emails present several significant challenges for email deliverability, especially during IP warming. First, they are a common tactic used by spammers to bypass text-based spam filters. Because of this, many ISPs and spam filters are inherently suspicious of emails with little to no text content and a disproportionately large image.
Second, engagement is critical for reputation. If recipients' email clients block images by default (a common setting), your entire message, including any calls to action, might be invisible. This leads to low open and click-through rates, which negatively impact your IP's reputation during the warming phase. Low engagement tells ISPs that your content isn't relevant or wanted, increasing the likelihood of future emails landing in the spam folder or on a blacklist (or blocklist).
ISPs analyze various factors including text-to-image ratio, link quality, and recipient behavior. An email that is 100% image lacks the textual context that filters use to assess relevance and trustworthiness. This makes it harder for them to accurately categorize your email stream, often leading to a conservative, spam-averse classification.
Text-heavy emails
Spam filter friendly: Provides clear content for spam filters to analyze, reducing false positives.
Higher engagement: Better visibility for recipients, even with images off, leading to more opens and clicks.
Consistent experience: Ensures that the warming content aligns with the actual marketing emails that will be sent.
Single-image emails
Spam trigger: Often flagged as suspicious by spam filters due to a lack of text.
Low engagement: Images may not load by default, resulting in poor visibility and user interaction.
Reputation risk: Negative engagement or filtering can hurt your IP's reputation, making future deliverability harder.
Best practices for IP warming content
For successful IP warming, the content of your emails should reflect the types of messages you plan to send regularly, but with an emphasis on maximum engagement. This means using a good text-to-image ratio, providing clear calls to action, and ensuring your emails are expected and wanted by recipients.
Consider starting your warm-up by sending highly engaging emails to your most active subscribers. These are recipients who are most likely to open, click, and reply, sending positive signals to ISPs. Gradually increase your sending volume and expand to less active segments over time, always monitoring your engagement metrics.
Ensure your emails have a healthy balance of text and images. A good rule of thumb is a 60:40 or 70:30 text-to-image ratio. Also, always include alt text for your images. This improves accessibility and provides context even if images are blocked. You want to make sure your warm-up content is compelling and useful to your audience from the outset.
Example of a balanced email structure for warmingHTML
<!DOCTYPE html>
<html>
<head>
<title>Email Subject Line</title>
</head>
<body>
<p>Dear [Recipient Name],</p>
<p>Here is some important text content that conveys value and encourages engagement.</p>
<img src="https://example.com/image.jpg" alt="Descriptive alt text for image" width="600" height="auto">
<p>More text to provide context and clear call to action.</p>
<a href="https://example.com/call-to-action">Click here to learn more</a>
<p>Best regards,</p>
<p>Your Team</p>
</body>
</html>
Key content best practices for IP warming
Text-to-image ratio: Aim for a higher proportion of text content to image content.
Clear calls to action: Ensure your email has clear, visible, and clickable calls to action, preferably text-based.
Engaged audience: Start warming with your most active and engaged subscribers.
Content consistency: Warm-up content should closely resemble the content you'll send after warming.
Strategic considerations for B2B sends
In a scenario where a B2B client has historically sent single-image emails and needs to migrate quickly, there's a delicate balance. While the risk might seem low for a monthly volume of 500K, using suboptimal content for IP warming can still set a poor foundation for your sender reputation. It's an opportunity to teach ISPs what your desirable email stream looks like.
The key challenge here is juggling the client's desire for a quick migration with the need to establish a strong email reputation. If the plan is to eventually transition to text-based content, it’s worth considering if that transition can begin during the warm-up phase. The content used for warming should be as representative as possible of the emails you intend to send in the long run.
Rushing the warm-up or using content that triggers spam filters (or leads to low engagement) can lead to future deliverability problems that are far more costly to fix than a slight delay in migration. It is often beneficial to invest time upfront in creating appropriate warm-up content that truly builds a positive reputation, rather than facing ongoing email deliverability issues down the line.
Views from the trenches
Best practices
Always include a healthy text-to-image ratio, providing context and reducing spam filter suspicion.
Start your warming efforts by sending to your most engaged subscribers who are likely to open and click.
Ensure the content used for warming is representative of the emails you will send long-term to establish an accurate reputation.
Common pitfalls
Sending emails that are primarily a single image, as this often triggers spam filters and reduces engagement.
Warming up to a low-engagement list, which can signal to ISPs that your emails are not desired by recipients.
Ignoring the content quality during warming, leading to a poor sender reputation despite increased volume.
Expert tips
Prioritize the long-term health of your sender reputation over quick migration timelines when content quality is a factor.
If current emails are single-image, use the warm-up period to introduce more text-based content proactively.
Educate clients on the importance of content quality for deliverability, especially during IP warming.
Expert view
Expert from Email Geeks says you can use single-image emails for warming, but they look like spam and have other issues, making them unsuitable for training machine learning systems about your mailstream content.
2021-02-05 - Email Geeks
Marketer view
Marketer from Email Geeks says in theory it's possible if the emails are expected and resonate, as IP warming is about demonstrating mailstream quality gradually.
2021-02-05 - Email Geeks
Summary
While technically possible to perform IP warming with single-image emails, it carries significant risks that can derail your deliverability efforts. The quality and composition of your emails during this critical phase directly influence your sender reputation. Prioritizing well-structured, engaging content with a healthy text-to-image ratio is paramount for success.
Even for clients accustomed to image-heavy emails, the IP warming period is an opportune moment to transition towards more deliverability-friendly content practices. Investing time in crafting appropriate warm-up emails will yield better inbox placement and overall email program success in the long run.
