Guides
How to Detect and Fix Factors Causing Promotional Email Flagging
Author :
MailMend Team
January 13, 2026
70% of emails show at least one spam-related issue, and for e-commerce brands relying on email marketing, landing in Gmail's Promotions tab instead of the Primary inbox can cost thousands in lost revenue. The challenge isn't just about writing better subject lines—it's about understanding the complex algorithmic factors that determine where your emails land. Solutions like Mailmend help e-commerce brands move campaigns from the Promotions tab to the Primary inbox without changing email content, but knowing what causes flagging in the first place is essential for any email marketer.
Key Takeaways
Gmail uses individual recipient behavior as the primary determinant of email placement—the same campaign can land in Primary for engaged subscribers but Promotions for inactive ones
Gmail and Yahoo implemented mandatory authentication requirements in February 2024 for bulk senders (5,000+ emails/day), including SPF, DKIM, and DMARC protocols
Senders with 90+ reputation scores achieve approximately 92% inbox placement, while those below 70 see less than 50%
Email lists decay at 22-25% annually (30% for B2B lists), yet a significant portion of senders rarely or never perform list cleaning
Poor list hygiene can cost approximately $42,000 per campaign for a 100,000-subscriber list
Using promotional ESPs and email prefixes like "info@" or "news@" significantly increases Promotions tab placement likelihood
Understanding Gmail's Promotional Tab Algorithm
Gmail's categorization system operates on multiple signals that determine whether your email reaches the Primary inbox or gets filtered to Promotions. Understanding these factors is the first step toward fixing deliverability issues.
The Science Behind Gmail's Filtering
Gmail analyzes four primary signals to categorize incoming emails:
Content similarity: How closely your email resembles known promotional messages (images, links, HTML formatting)
Sender reputation: Your historical track record for sending promotional versus personal content
Recipient behavior patterns: How similar recipients typically interact with content like yours
Individual engagement history: How the specific recipient has engaged with your emails in the past
The critical insight here is that email placement is personalized. A campaign you send today might reach the Primary inbox for subscribers who frequently open and click your emails, while landing in Promotions for those who haven't engaged recently.
Identifying Your Promotional Threshold
Every sender has what deliverability experts call a "promotional threshold"—the combination of factors that tips Gmail's algorithm toward categorizing emails as promotional. This threshold varies based on:
Your sending domain's age and history
The engagement rates of your subscriber base
The technical infrastructure you use for sending
Content patterns across your email campaigns
With approximately half of Gmail users utilizing the tabbed inbox feature, landing in the right tab is crucial. Emails in the Promotions tab receive 12% less engagement than those in Primary. However, it's worth noting that 79.7% of users check their Promotions tab weekly, with 51% checking daily.
Common Triggers for Promotional Email Flagging
Multiple factors contribute to promotional flagging, spanning content, technical setup, and sender behavior.
Content-Related Flags
Certain email characteristics dramatically increase promotional flagging:
Excessive images and HTML: Heavy visual formatting signals marketing content
High link density: Multiple links suggest promotional intent
Spam trigger words: Terms like "free," "urgent," and "guarantee" elevate risk
All-caps text and excessive punctuation: These patterns trigger spam filters
Image-to-text ratio imbalance: Too many images relative to text raises flags
Sender Reputation and Deliverability
Your sender reputation operates like a credit score, calculated on a 0-100 scale based on seven core factors:
Authentication setup (SPF, DKIM, DMARC)
Bounce rates (must stay below 2%)
Spam complaints (must stay below 0.3%, with 0.1% recommended)
Recipient engagement levels
List hygiene quality
Sending history and volume consistency
Content quality
Technical Configuration Pitfalls
Infrastructure choices significantly impact categorization. Using promotional ESPs like SendGrid, Brevo, Mailgun, or Mailchimp automatically signals Gmail to categorize emails as promotional. Similarly:
Email prefixes like "info@," "news@," "promotions@," or "hello@" are strongly associated with promotional content
Sender names showing only brand names (not personal names) increase promotional categorization
Domains without proper authentication face automatic filtering
Auditing Your Current Email Deliverability Status
Before implementing fixes, you need to understand where your emails currently land and why.
Benchmarking Your Performance
A comprehensive deliverability audit should examine:
Inbox placement rates: What percentage of emails reach Primary versus Promotions versus spam?
Bounce rates: Are you exceeding the 2% threshold?
Spam complaint rates: Are complaints above the 0.3% maximum?
Engagement metrics: How do open rates and click-through rates compare to industry benchmarks?
According to Carin Slater, Manager of Lifecycle Email Marketing at Litmus: "Everyone's goal is obviously 100% inbox placement. We want 100% of our emails getting to the inbox, and if it drops below 90%, we're going to immediately investigate what's going on."
Leveraging ESP Analytics for Insights
Your email service provider's reporting tools reveal critical diagnostic information:
Delivery rates by inbox provider (Gmail, Yahoo, Outlook)
Engagement trends over time
List growth and decay patterns
Authentication status and errors
22% of marketers don't measure deliverability at all—a significant gap when email delivers an average $36 ROI per $1 spent.
Strategies for Improving Primary Inbox Placement
Once you've identified the factors affecting your deliverability, you can implement targeted fixes.
Building Positive Sender Signals
The most sustainable path to Primary inbox placement involves building genuine engagement:
Encourage replies: Build natural moments into email campaigns that prompt real responses like "What's your biggest challenge right now?" These interactions help build relationships and signal to email providers like Gmail that people want to read your emails.
Segment by engagement: Send to your most active subscribers first to build positive signals
Maintain consistent sending schedules: Erratic volume changes trigger algorithmic scrutiny
Request whitelist additions: Ask subscribers to move emails to Primary and add you to contacts
List Hygiene as Revenue Protection
Email lists naturally decay at 22-25% annually (30% for B2B lists), yet a significant portion of senders rarely or never perform list cleaning. The financial impact is substantial: senders with hygiene scores above 95% achieve 97% inbox placement versus only 76% for those below 85%.
Immediate removal criteria should include:
Hard bounces after a single occurrence
Spam complainers instantly
Invalid syntax or typos
Confirmed closed accounts
Subscribers inactive for 6-12 months
Regular list cleaning improves open rates by 50% and click-through rates by 75% compared to neglected lists.
Authentication Requirements
Gmail and Yahoo's 2024 requirements mandate proper authentication for bulk senders:
SPF (Sender Policy Framework): Authorizes which servers can send email for your domain
DKIM (DomainKeys Identified Mail): Provides cryptographic verification of email authenticity
DMARC (Domain-based Message Authentication): Tells receiving servers how to handle authentication failures
While DMARC adoption rates are high among the largest companies, with a 2026 report from EasyDMARC showing 93.8% of Fortune 500 companies have a DMARC record, gaps may still exist in enforcement and among smaller businesses.
Leveraging A/B Testing for Deliverability and Revenue Growth
Measuring the impact of inbox placement changes requires systematic testing.
Measuring the Impact of Inbox Placement
Split testing allows you to isolate the revenue impact of Primary versus Promotions placement:
Open rate differences: How much higher are opens when emails land in Primary?
Click-through rate variance: Does Primary placement increase clicks?
Revenue attribution: Can you trace higher revenue to improved placement?
ROI improvement: What's the overall return on deliverability investments?
Continuous Optimization with Data
Deliverability isn't a one-time fix. Ongoing monitoring should track:
Week-over-week placement trends
Engagement patterns by subscriber segment
Impact of content changes on categorization
Seasonal variations in deliverability
Why Traditional Deliverability Solutions Fall Short
Most conventional approaches to fixing promotional email flagging require significant time and resource investment.
The Limitations of Content-Based Approaches
Traditional deliverability consulting typically requires:
Comprehensive email strategy overhauls
Content and copywriting modifications
Weeks or months of domain warming
Complex technical infrastructure changes
These methods address real issues but demand substantial workflow disruptions. For seven-to-eight-figure e-commerce brands running continuous campaigns, pausing operations for deliverability fixes isn't always feasible.
Time and Resource Intensive Methods
Domain warming alone can take 4-8 weeks before seeing improvements. Content strategy changes require testing cycles. Technical reconfigurations need IT resources and careful implementation to avoid breaking existing systems.
The gap in the market has been solutions that improve inbox placement without requiring these extensive changes.
Mailmend: A Zero-Change Solution for E-commerce Deliverability
Mailmend offers an alternative approach to the deliverability problem—one that doesn't require content modifications, copywriting adjustments, or complex technical setup.
How Mailmend Works
Mailmend's proprietary technology operates through a three-step process:
Testing: Sends client emails to a rotating set of test inboxes to determine current placement
Analysis: Uses proprietary AI to analyze the "promotional threshold"—the combined factors Gmail's algorithms use to categorize emails
Custom code generation: Creates account-specific code that counteracts promotional categorization signals
The solution integrates as a drag-and-drop code snippet into Klaviyo templates, completing setup in under 5 minutes.
Immediate, Measurable Impact
Unlike traditional solutions requiring weeks of implementation, Mailmend delivers Day 1 results. The platform enables brands to conduct A/B testing within Klaviyo to measure exact performance lift from Primary inbox placement versus Promotions tab placement.
Client case studies demonstrate consistent results:
Dr. Squatch: Increased their email revenue by 112% escaping the promotions tab. In just 24 hours, Dr. Squatch ran a test to see how Mailmend was performing. Little did they know they were missing out on half the revenue they deserved. 42% increase in open rates and 67% increase in CTR.
StickerYou: "Day 1 boost of 20% - 100% increase by month 1." StickerYou was absolutely blown away by the results of Mailmend. After going through our videos and speaking to our team, they signed up. 64% increase in open rates and 43% increase in CTR.
Ministry of Supply: "Results within a business day!" Although skeptical at first, Ministry Of Supply was able to quickly get setup with Mailmend in a matter of business days and land in the inbox! 27% increase in open rates and 30% increase in CTR.
Larsson & Jennings: Saved their Black Friday. Anna was suffering from low open rates and click rates after they had a data failure in their ESP. They also had massive promotions tab issues. Mailmend came in and fixed all of it. 82% increase in open rates and 51% increase in CTR.
Amberjack: "It Actually Worked." Blake was looking for more incremental revenue after they noticed click rates take a dive. They ran some tests with Mailmend and instantly saw revenue shoot up. 54% increase in open rates and 51% increase in CTR.
Clevr Blends: Made a big difference. Clevr Blends was looking for an easy way to boost their email revenue after seeing low opens and clicks - so they came to Mailmend and saw amazing results. 21% increase in open rates and 63% increase in CTR.
Partnership Model for Success
Mailmend operates on a revenue satisfaction guarantee with 1-to-1 client relationships through dedicated representatives. Each client works directly with a team member who manages implementation and ongoing optimization.
For brands preparing for Black Friday/Cyber Monday, launching new products, or running seasonal campaigns where inbox placement directly impacts revenue, Mailmend offers a path to 50-100% increases in email revenue. Contact Mailmend to see how their solution performs with your specific Klaviyo account.
Maximizing E-commerce Revenue with Optimized Inbox Placement
For e-commerce brands, email deliverability directly correlates with revenue performance. When emails reach the Primary inbox, they appear at the top of recipients' inboxes and receive significantly higher visibility and engagement.
The Promotions tab isn't a death sentence—as industry experts note, it's still part of the inbox and certainly better than landing in the spam folder.
However, for brands running aggressive promotional strategies during peak seasons, the difference between Primary and Promotions placement can mean tens of thousands in revenue variation per campaign.
Frequently Asked Questions
What specifically causes my emails to land in Gmail's Promotions tab?
Gmail uses four primary signals: content similarity to known promotional messages (images, links, HTML formatting), your historical sender reputation, overall recipient behavior patterns with similar content, and the individual recipient's past engagement with your emails. The algorithm is user-specific, meaning the same email can land in Primary for engaged subscribers but Promotions for inactive ones.
How quickly can I expect results from improving my email deliverability?
Traditional approaches like domain warming and content strategy changes typically require 4-8 weeks to show improvements. Solutions like Mailmend that work at the technical/header level rather than content level can deliver results on Day 1 of implementation, as demonstrated by clients achieving significant performance increases within 24 hours.
Does fixing promotional email flagging require significant changes to my existing email content or strategy?
Not necessarily. While traditional deliverability consulting often requires comprehensive content modifications, workflow changes, and technical reconfigurations, algorithmic solutions can improve inbox placement without altering email content, copy, or technical infrastructure. This allows brands to maintain their existing email marketing workflows while achieving better deliverability.
Can I measure the exact impact of moving emails to the Primary inbox on my revenue?
Yes. Platforms like Klaviyo enable A/B testing where you can split test emails and measure open rate differences, click-through rate variance, and revenue attribution between Primary and Promotions placement. This data allows you to quantify the exact ROI impact of improved deliverability.
Is Mailmend compliant with email marketing regulations?
Mailmend undergoes compliance reviews before implementation, with clients reviewing all compliance documents prior to installation. The technology operates at the technical/header level through code modification rather than content manipulation, integrating with Klaviyo's established infrastructure. For partnership inquiries or compliance questions, brands can work directly with dedicated Mailmend representatives.
