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Email Deliverability Test and Spam Rate Optimization Guide

Deliverability tests are an invaluable tool for monitoring, evaluating, and improving your email deliverability.

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Deliverability Test Overview

The Deliverability Test sends a personalized message to mailboxes outside the warm-up network to determine your inbox placement.

  • Provider Selection: Test with relevant B2B (G Suite, MS 365, SMTP) or B2C (Gmail, Outlook, Yahoo, Zoho) providers based on your target audience.
  • Deliverability Score (ISP Score): Indicates the likelihood of your emails reaching the inbox based on your last test.
  • Credits: Shared across all mailboxes. Each subscription includes at least one test per month.

Auto-Test Configuration

Auto-Test runs automatically once a week for selected domains or mailboxes. Test times are system-determined, but the day is user-selected.

  • For Domains: Navigate to the Dashboard, select a domain, click Inbox Placement Test, toggle Auto-Test, and select a day (or use Auto-Pick).
  • For Mailboxes: Navigate to the Mailbox tab, select the mailbox, scroll to Auto-Test, and configure the day.
  • Workspace Level: Auto-Test can also be configured for all mailboxes at once via Workspace Settings. This allows you to set a default auto-test schedule that applies across your entire workspace without configuring each mailbox individually.

Campaign Placement Test

In addition to the standard deliverability test, Warmy offers a dedicated Campaign Placement Test feature — designed specifically to test how your actual campaign emails perform across providers before you send them at scale. This is especially useful for validating template content, links, and subject lines prior to a major send. 

Interpreting Results

  • Inbox / Promotions: The message was delivered successfully.
  • Spam: The message was routed to the junk folder.
  • Unreceived: A sending or tracking error occurred.
  • Blacklists: Indicates if your sending IP is listed. If using a shared server (e.g., standard Gmail/Outlook) or a new domain, being listed is common, usually temporary, and rarely requires action.

Action Plan for Test Results

  • If results are good: Continue monitoring metrics (open rates, clicks), conduct A/B tests to optimize content, and respect opt-outs to maintain list hygiene.
  • If results are bad:
    • Verify SPF, DKIM, and DMARC authentication.
    • Clean your email lists.
    • Use template warm-ups.
    • Process spam complaints and unsubscribes immediately.
    • Check ISP-specific guidelines (e.g., Gmail Postmaster Tools).

High-Volume Sending Insights

  • Volume Control: For campaigns exceeding 1,000 emails/day, maintain a minimum 1:1 ratio between warm-up emails and campaign emails. For cold email campaigns, a 2:1 warm-up to campaign ratio is recommended for best results.
  • Gmail & Google Workspace: Google uses engagement-based filtering. Spam complaint rates above 0.10% can begin to affect deliverability, and rates above 0.30% will cause significant inbox placement drops. Google Postmaster Tools is essential for monitoring domain and IP reputation in real time.
  • Microsoft 365 & Outlook: Microsoft employs aggressive AI-based filtering (SmartScreen). New domains or IPs sending to Outlook/Hotmail/Live can expect initial deliverability challenges lasting 4–8 weeks. Sending more than 20–30 emails/day to Outlook from a cold domain can trigger rate limiting or blocks. Recovery from poor reputation with Microsoft typically takes 4–8 weeks of consistent warm-up.
  • Yahoo & AOL: Yahoo uses strict complaint-based filtering. Sending more than 15–20 emails/day to Yahoo from a new or low-reputation domain can trigger a 24-hour block. Yahoo has adopted Google's spam complaint threshold guidelines (0.10%/0.30%), making list hygiene critical.
  • Zoho: Generally more lenient than Microsoft or Yahoo, but still sensitive to authentication issues. Ensure SPF, DKIM, and DMARC are properly configured before sending at volume.
  • General Best Practices for High Volume:
    • Always warm up for at least 4–6 weeks before launching large campaigns
    • Never increase daily send volume by more than 20–30% per day
    • Monitor bounce rates closely — hard bounce rates above 2% can severely damage domain reputation
    • Use separate domains for transactional and marketing emails
    • Segment your list and prioritize engaged subscribers
  • Troubleshooting: Monitor bounce emails constantly. Contact support for custom warm-up adjustments targeted at specific strict providers.

Conclusion

Email deliverability requires constant monitoring. If you encounter high bounce rates or need a custom warm-up strategy for strict providers, our support team is ready to help.

Need help? Schedule a call with us 👨🏻‍💻