What causes newsletters to be categorized as promotional in Gmail after an ESP migration?
Matthew Whittaker
Co-founder & CTO, Suped
Published 23 Apr 2025
Updated 19 Aug 2025
8 min read
It can be incredibly frustrating when your perfectly crafted newsletters, which have always landed in the primary inbox, suddenly start appearing in Gmail's promotions tab right after you've migrated to a new Email Service Provider (ESP). You might wonder if the migration itself is the culprit, and while it's not always the direct cause, it often acts as a significant trigger for Gmail to re-evaluate how it categorizes your emails.
This shift in categorization can have a noticeable impact, especially if your business relies on open rates for sponsorships or engagement metrics. When subscribers don't immediately see your newsletter in their primary inbox, it can lead to decreased visibility and engagement, directly affecting your bottom line. It's a common concern, and many senders experience this challenge.
The good news is that understanding why this happens is the first step toward fixing it. It involves a mix of how Gmail's sophisticated algorithms work, the technical nuances of your new ESP, and the ongoing relationship you have with your subscribers. Let's explore the factors at play and what you can do to guide your newsletters back to where they belong.
Understanding Gmail's categories
Gmail employs a complex system to categorize incoming emails, aiming to provide users with a clean and organized inbox. This system divides emails into various tabs, including Primary, Social, Promotions, and Updates. The goal is to help users prioritize their communications and reduce inbox clutter. Promotional content, by design, often finds its way into the Promotions tab.
Gmail's categorization relies on a multitude of signals. These include the sender's reputation, domain authentication, the content of the email itself (keywords, images, links), and crucially, subscriber engagement. If your subscribers consistently open, click, and interact positively with your emails, or even move them to their primary inbox, Gmail learns to deliver them accordingly.
While the Promotions tab is not the spam folder, and Gmail suggests it helps improve open rates for marketing messages, it's undeniable that many users prioritize their Primary tab. For a daily newsletter, especially one with informational content like politics or news, a sudden shift to the Promotions tab can significantly impact its visibility and, by extension, its value to sponsors who measure opens. You can learn more about how Gmail automatically sorts emails into categories on Google's support page.
The migration trigger
When you migrate to a new ESP, you're essentially changing the infrastructure from which your emails are sent. This change, even if subtle, can cause Gmail to re-evaluate your sender profile. It's akin to moving into a new house; even if you're a responsible person, the new neighborhood still needs to get to know you before fully trusting you.
Before migration
Established reputation: Gmail has years of data on your sending patterns and subscriber engagement from your previous ESP.
Stable IP addresses: Your emails are sent from IP addresses with a known and trusted history with Gmail.
Consistent technical setup: Authentication, headers, and footers have been consistent, providing a clear signal.
After migration
New IP addresses: Even if dedicated, these IPs need to build their own reputation. Shared IPs inherit the reputation of other senders.
Altered email structure: New ESPs might inject different tracking pixels, change unsubscribe link formats, or add their own boilerplate text.
Re-evaluation: Gmail's algorithms initiate a re-assessment of your sending patterns and content, looking for promotional indicators.
A crucial aspect here is the concept of IP warming. Even if your domain has a sterling reputation, emails sent from new IP addresses will typically undergo a warming period. During this time, mailbox providers, including Gmail, observe the sending patterns and engagement signals from the new IP. If a large volume of email is sent too quickly from a new IP, it can trigger spam filters or, in this case, push emails to the Promotions tab. You can find more information on what causes emails to go to spam when migrating to a new ESP.
Key technical and content shifts
Beyond IP warming, the actual technical setup and the content itself play significant roles. Your new ESP might implement authentication protocols (like SPF, DKIM, and DMARC) differently, or introduce new elements into your email's structure. These changes, even if minor, can influence how Gmail perceives your messages. A proper understanding of DMARC, SPF, and DKIM is crucial.
New ESP features and their impact
Boilerplate text: Many ESPs add standard footers like 'This email was sent by...' or their branding. This text can sometimes signal a marketing message.
Tracking pixels and links: New ESPs use different domains for link wrapping and open tracking. Gmail analyzes these domains and their associated reputation.
Unsubscribe mechanisms: The specific type of unsubscribe link and its placement can also be a factor in Gmail's categorization.
To identify if these technical shifts are affecting your deliverability, reviewing your email headers is a key step. You can compare headers from emails sent by your old ESP versus your new one to spot differences in authentication, tracking domains, and other added elements.
Example of an email header from a new ESPemail-header
Received: from mail.newesp.com (mail.newesp.com [198.51.100.10])
by mx.google.com with ESMTPS id abc123def456; Thu, 1 Jan 2024 12:00:00 -0800
Authentication-Results: mx.google.com;
dkim=pass header.i=@yourdomain.com header.s=newespkey;
spf=pass (google.com: domain of yourdomain.com designates 198.51.100.10 as permitted sender) smtp.mailfrom=yourdomain.com;
dmarc=pass (p=none dis=none) header.from=yourdomain.com
Content-Type: text/html; charset="UTF-8"
List-Unsubscribe: <https://newesp.com/unsubscribe/abcDEF>, <mailto:unsubscribe-abcDEF@newesp.com>
X-Mailgun-Sid: youruniquesid
Even for seemingly informational newsletters, Gmail's content filters are always at work. They scan for keywords, image-to-text ratios, the number and type of links, and the overall 'look and feel' of the email. If the email resembles typical marketing emails, even if it's news, it might be categorized as promotional. For instance, a newsletter with many calls to action, prominent images, or heavy use of marketing language could be flagged. This is why some newsletters are consistently in the promotions tab. For more insight into how Gmail makes these decisions, consider reviewing information on how Gmail decides what goes to promotions.
Strategies for better inbox placement
To mitigate the risk of your newsletters landing in the promotions tab after an ESP migration, a proactive approach is essential. Start by ensuring your domain's email authentication records (SPF, DKIM, DMARC) are correctly configured for your new ESP. These foundational elements are critical for establishing trust with mailbox providers.
Next, critically review your newsletter's content and design. While it might have been fine with your previous ESP, the new sending environment could trigger different filters. Minimize overtly promotional language, reduce the number of high-density promotional images, and ensure a healthy text-to-image ratio. If your newsletter contains advertisements, consider how they are visually integrated and worded. Sometimes, small changes can make a big difference in how Gmail interprets your content. You can explore more reasons why your emails might go to the promotions tab.
Encourage subscriber engagement. A proactive step is to ask your subscribers to drag your emails from the promotions tab to their primary inbox. This sends a strong positive signal to Gmail. You can include a small note in your welcome email or post-signup page, instructing new subscribers to do this. A pro tip regarding this is to guide them through the process in a friendly way. Also, prompt them to add your sending address to their contacts.
Finally, consistent monitoring of your deliverability is vital. Utilizing tools like Google Postmaster Tools can provide valuable insights into your domain and IP reputation, spam rate, and other key metrics directly from Gmail's perspective. This data will help you identify issues early and make informed adjustments. Regular review of these tools can help you maintain good standing and ensure your newsletters reach the primary inbox. Learn how to improve domain reputation using Google Postmaster Tools.
Views from the trenches
Best practices
Ensure SPF, DKIM, and DMARC are properly configured by your new ESP and align with your sending domain.
Gradually increase sending volume (warm-up) when using new IP addresses, even if they are dedicated.
Review your email content for promotional signals and aim for a balance of informational vs. marketing elements.
Actively encourage subscribers to move your emails to their primary inbox and add you to their contacts.
Common pitfalls
Assuming deliverability will remain the same after an ESP migration without a warming period.
Overlooking boilerplate text or new tracking links introduced by the new ESP that can trigger promotional flags.
Not monitoring Gmail Postmaster Tools for changes in sender reputation or deliverability metrics post-migration.
Ignoring subtle content changes that, in combination with a new sending environment, can shift categorization.
Expert tips
"Test thoroughly with seed lists across various Gmail accounts to see where your emails land before full deployment."
"Segment your audience. Highly engaged subscribers can help 'train' Gmail to recognize your emails as primary."
"Keep your email list clean. Removing unengaged subscribers reduces the risk of hitting spam traps and boosts overall deliverability."
"Consider A/B testing different subject lines and content variations to see what performs best in terms of primary inbox placement."
Expert view
Expert from Email Geeks says it's not likely the sole cause, but the ESP migration can certainly be a contributing factor, especially if the new provider adds specific code, link tracking, or boilerplate text to the messages.
2018-09-27 - Email Geeks
Expert view
Expert from Email Geeks says the fundamental question remains whether the content itself is promotional, as this is a primary driver for Gmail's categorization.
2018-09-27 - Email Geeks
Moving forward with confidence
Migrating to a new ESP is a significant step, and it's understandable for deliverability metrics, like Gmail inbox placement, to experience a temporary shift. While your newsletters may have consistently landed in the primary tab before, the new sending environment prompts Gmail to re-evaluate your email stream. This re-evaluation considers everything from your new sending IPs and authentication setup to subtle changes in your email's code and content.
The key to successfully navigating this challenge is a combination of technical diligence and strategic content optimization. By ensuring proper authentication, warming your new IPs, and adapting your content to minimize promotional signals, you can proactively guide your newsletters back to the primary inbox. Continuous monitoring and a focus on fostering strong subscriber engagement will solidify your sender reputation and help you achieve consistent inbox placement, ensuring your valuable content reaches your audience effectively.
Gmail's perspective. This data will help you identify issues early and make informed adjustments. Regular review of these tools can help you maintain good standing and ensure your newsletters reach the primary inbox. Learn how to improve domain reputation using Google Postmaster Tools.
