Open rates tell you who engaged. Inbox placement testing tells you who had the chance to engage. The difference matters. If Gmail puts your email in the Promotions tab, or Yahoo sends it to spam, your open rate drops not because of your content but because of placement.

Inbox placement testing sends your email to seed addresses across major email providers (Gmail, Outlook, Yahoo, Apple Mail) and checks where it lands: primary inbox, promotions/updates tab, spam folder, or not delivered at all. This lets you identify deliverability problems before they affect your real subscribers.

How Inbox Placement Testing Works

Seed addresses: A network of test email addresses across Gmail, Outlook, Yahoo, and other providers
Send a test: Send your campaign to these seed addresses before sending to your list
Check placement: The tool checks where each email landed (inbox, spam, promotions, updates)
Report: See placement rates by provider, spam filter results, and authentication status
Fix and resend: If placement is poor, adjust content, authentication, or sending infrastructure and test again

The 6 Best Options

1. Sequenzy

Best for: SaaS companies wanting built-in deliverability monitoring with email marketing

Sequenzy includes inbox placement monitoring as part of its email platform. Before sending campaigns, run a placement test to see where your email lands across Gmail, Outlook, Yahoo, and Apple Mail. Results show inbox vs. spam placement, authentication status (SPF, DKIM, DMARC), and content analysis.

The advantage over standalone tools is integration. When Sequenzy detects placement issues, it surfaces recommendations directly in your campaign workflow. Poor Gmail placement? The platform suggests content adjustments before you send to your full list. Authentication problems? Sequenzy flags them in your domain settings.

For SaaS companies sending lifecycle email, placement monitoring is especially critical. Your dunning emails, trial conversion sequences, and onboarding flows only work if they reach the inbox. Sequenzy monitors placement for both transactional and marketing email in one platform.

Provider coverage: Gmail, Outlook, Yahoo, Apple Mail, and more Features: Inbox placement testing, authentication analysis, content scoring, deliverability dashboard Pricing: From $29/month (included in all plans) Pros: Built into email platform, no separate tool needed, covers transactional and marketing Cons: Less comprehensive than dedicated tools like GlockApps for edge-case providers

2. GlockApps

Best for: Dedicated inbox placement testing with the broadest provider coverage

GlockApps is a standalone deliverability testing platform that checks inbox placement across 30+ email providers worldwide. Send a test email and see exactly where it lands on Gmail, Outlook, Yahoo, AOL, and dozens of regional providers.

Beyond placement testing, GlockApps checks DMARC, SPF, and DKIM authentication, analyzes content for spam triggers, and provides sender reputation monitoring. For teams that want a dedicated deliverability monitoring tool alongside their email platform, GlockApps is the most comprehensive option.

Provider coverage: 30+ email providers globally Features: Inbox placement, spam testing, authentication analysis, content analysis, reputation monitoring Pricing: From $59/month Pros: Broadest provider coverage, detailed analysis, authentication checks, standalone tool Cons: Separate cost from your email platform, requires manual testing workflow

3. Mailgun (Inbox Placement)

Best for: Built-in inbox placement testing within email infrastructure

Mailgun includes inbox placement testing as a feature within the platform. Send test campaigns to Mailgun's seed list network and see placement results by provider. The integration means you don't need a separate tool. Results appear in the same dashboard where you manage your sending.

The testing covers major providers and includes authentication analysis and content scoring. For teams already using Mailgun for email infrastructure, the built-in placement testing eliminates the need for a separate monitoring tool.

Provider coverage: Major providers (Gmail, Outlook, Yahoo, etc.) Features: Inbox placement, authentication analysis, content scoring, integrated with sending Pricing: Included in Scale and Custom plans Pros: Built into email platform, no separate tool needed, major provider coverage Cons: Less comprehensive than dedicated tools, only available on higher plans

4. Mail-Tester

Best for: Quick, free deliverability checks for individual emails

Mail-Tester provides a simple, free deliverability check. Send an email to a unique Mail-Tester address and get a score out of 10, with detailed feedback on authentication, content, blacklist status, and potential spam triggers. It's not full inbox placement testing, but it's the fastest way to check if your email has obvious problems.

For quick sanity checks before major campaigns, Mail-Tester is invaluable. It catches authentication issues, content problems, and blacklist entries that would hurt deliverability. The free tier allows a few tests per day.

Provider coverage: General deliverability score (not per-provider placement) Features: Spam score, authentication check, blacklist check, content analysis Pricing: Free (limited tests), from $30/year for unlimited Pros: Free, instant results, easy to use, catches obvious problems Cons: Not true inbox placement testing, general score not per-provider, limited free tests

5. Litmus

Best for: Email previews combined with deliverability testing

Litmus is primarily an email testing tool for rendering and design (see how your email looks in 90+ email clients). But it also includes a spam testing feature that checks your email against major spam filters and provides deliverability guidance.

The combination of rendering testing and spam testing makes Litmus valuable for teams that want to check both how their email looks and whether it'll reach the inbox. The workflow integrates into the campaign creation process: design, preview, test deliverability, then send.

Provider coverage: Major spam filters (SpamAssassin, Barracuda, etc.) Features: Spam filter testing, email rendering previews, authentication checks, analytics Pricing: From $99/month Pros: Rendering + deliverability in one tool, spam filter testing, comprehensive previews Cons: Expensive, spam filter testing is not the same as inbox placement, primarily a preview tool

6. Amazon SES (Virtual Deliverability Manager)

Best for: Built-in deliverability monitoring for AWS email infrastructure

Amazon SES's Virtual Deliverability Manager (VDM) provides automated deliverability monitoring and optimization. While not traditional inbox placement testing, VDM monitors your sending reputation, delivery rates, and engagement metrics in real-time. It identifies potential deliverability issues and provides recommendations.

For teams already on SES, VDM provides deliverability intelligence without a third-party tool. The advisor feature suggests specific actions to improve delivery rates based on your sending patterns and reputation data.

Provider coverage: Overall deliverability monitoring (not per-provider placement) Features: Reputation monitoring, delivery rate tracking, advisor recommendations, automated alerts Pricing: $0.05 per 1,000 emails monitored (add-on to SES) Pros: Built into SES, automated monitoring, proactive recommendations, low cost Cons: Not traditional inbox placement testing, AWS-only, monitoring not testing

When to Test Inbox Placement

Before Major Campaigns

Always test before sending to your full list if:

You're sending to a large segment (5,000+ subscribers)
You've changed your sending infrastructure (new domain, new IP, new platform)
Your last campaign had unusual engagement drops
You're sending a different type of content than usual

After Infrastructure Changes

Test placement whenever you:

Set up a new sending domain or subdomain
Migrate to a new email platform
Start using a new dedicated IP
Update DNS records (SPF, DKIM, DMARC)

On a Regular Schedule

For active senders:

Weekly placement tests catch gradual reputation degradation
Monthly at minimum for teams sending regular campaigns
After any deliverability incident (bounce spike, spam complaint spike)

Improving Poor Inbox Placement

If testing reveals poor placement, investigate in this order:

Authentication: Verify SPF, DKIM, and DMARC are correctly configured. Failed authentication is the most common cause of spam placement.
Reputation: Check if your sending domain or IP is on any blacklists. Use tools like MXToolbox to check blacklist status.
Content: Review for spam trigger words, excessive images, misleading subject lines, or missing unsubscribe links.
Engagement: If specific providers (like Gmail) flag you, your engagement rates with their users may be low. Send only to engaged Gmail users to rebuild reputation.
List quality: High bounce rates or spam complaints indicate list hygiene problems. Clean your list and remove unengaged subscribers.

FAQ

How accurate is inbox placement testing? Seed-based testing is directional, not exact. The seed addresses may not perfectly represent how email providers treat your actual subscribers. But it reliably catches major issues (spam placement, authentication failures, blacklisting) and shows trends over time.

Can I test inbox placement for free? Mail-Tester offers free basic tests (deliverability score, not per-provider placement). For actual inbox placement testing across providers, paid tools are required. GlockApps offers limited free testing.

How often should I test? Before major campaigns (always). Weekly if you send multiple campaigns per week. Monthly at minimum for regular senders. After any infrastructure change immediately.

Does Promotions tab placement count as delivered? Yes, technically. Gmail's Promotions tab is part of the inbox, not spam. But engagement rates from the Promotions tab are significantly lower than the Primary tab. If you're testing placement, note the tab placement, not just inbox vs. spam.

Can inbox placement testing itself hurt my deliverability? No. The test volume is tiny (dozens of emails, not thousands) and the seed addresses are legitimate. Testing does not affect your sending reputation.