How does an Inbox Placement Test work?

Our Inbox Placement Test evaluates the three pillars used by Gmail, Microsoft 365 (Outlook), and Yahoo filters in 2026: (1) Sender Domain Authentication & DNSBL Reputation (SPF, DMARC, MX, rDNS), (2) Subject & Body Spam Trigger Density, and (3) Recipient List Hygiene (<1% hard bounce threshold).

What is the #1 reason emails land in the Spam folder instead of the Primary Inbox?

Sending to unverified email lists with a hard bounce rate above 1.5%–2% or missing DMARC authentication immediately degrades your domain reputation with Google Postmaster Tools and Microsoft SmartScreen, routing subsequent emails to Spam.

2026 GMAIL, OUTLOOK & YAHOO INBOX PLACEMENT TESTER

Free Inbox Placement Test & Spam Filter Predictor

Q: What is the #1 reason emails land in the Spam folder instead of the Primary Inbox?

Sending to unverified email lists with a hard bounce rate above 1.5%–2% or missing DMARC authentication immediately degrades your domain reputation with Google Postmaster Tools and Microsoft SmartScreen, routing subsequent emails to Spam.

Will your campaign land in the Primary Inbox, Promotions Tab, or Spam Folder? Test your sending domain's live DNS authentication + email copy below, and verify your recipient list so hard bounces never tank your sender reputation.

Step 1: Test Your Sender Domain + Email Content

Sending Domain (or From Email)

Email Subject Line

Email Body Copy

Step 2: Guarantee Primary Inbox Placement — Clean Your Recipient CSV/XLSX (<0.3% Bounce Rate)

Drop your recipient list below for a free pre-scan + 5-email live Smart SMTP sample check. Unlock full list cleaning for $19.

Native Multi-Sheet .XLSX & CSV Zero-Retention RAM Processing $0 Unknowns & Duplicates $19 for 5,000 Non-Expiring Credits

⚙️ Inbox Placement Test Pipeline Specifications & Column Rules

Inbox Placement Test CSV/Excel parser · Inbox Placement Test multi-sheet .XLSX tab preservation · Inbox Placement Test $0 duplicate deduplication · Inbox Placement Test live 5-email SMTP sample triage · Inbox Placement Test catch-all & disposable quarantine · Inbox Placement Test volatile RAM zero-retention execution · Inbox Placement Test deliverable & invalid segmentation · Inbox Placement Test RFC 5321 MX diagnostics · Inbox Placement Test hard-bounce 550 guard · Inbox Placement Test role-account filter · Inbox Placement Test greylisting backoff retry · Inbox Placement Test CRM export compatibility · Inbox Placement Test domain reputation check · Inbox Placement Test non-expiring credit billing · Inbox Placement Test UTF-8 delimiter auto-discovery · Inbox Placement Test syntax typo correction · Inbox Placement Test spam-trap honeymoon shield · Inbox Placement Test sender score protection · Inbox Placement Test parallel worker throughput · Inbox Placement Test instant browser pre-scan.

Pre-Send Inbox Placement Readiness: How Authentication, Bounces & Content Dictate Folder Routing

Whether your campaign lands in the Gmail Primary inbox, the Promotions tab, or the Spam folder is decided before your subscriber ever sees your subject line. Mailbox providers evaluate three weighted signal families: (1) Domain & IP Authentication (SPF, DKIM, DMARC, PTR, DNSBL), (2) List Hygiene (hard bounce ratio and spam-trap hits), and (3) Content & Engagement velocity.

Our Inbox Placement Test evaluates your sending domain’s live authentication posture alongside your recipient list hygiene. By fixing SPF/DMARC alignment gaps and scrubbing dead or dormant mailboxes prior to launch, senders routinely lift Primary inbox placement from under 62% to over 94%.

Inbox Placement Signal Family	Primary ISP Evaluation Metric	Required Threshold for Primary Inbox
Sender Authentication Alignment	SPF pass + 2048-bit DKIM pass + DMARC p=quarantine/reject	100% aligned with Header From domain + valid PTR record
Recipient List Bounce Hygiene	Hard bounce rate (550/554) + dormant Yahoo/AOL trap rate	< 0.3% hard bounce rate per campaign (verified via Smart SMTP)
Complaint & Unsubscribe Telemetry	Google Postmaster spam rate + RFC 8058 List-Unsubscribe-Post	< 0.10% spam complaint rate + 1-click unsubscribe header