# Deliverability Diagnosis
## How to Use This File
Reference this file when a user says their emails are landing in spam, their reply rates have dropped, their bounce rates are climbing, or they suspect something is wrong with their deliverability. This is the diagnostic and troubleshooting reference. Walk them through the 4-Checkpoint Pre-Send Evaluation first, then use the troubleshooting trees to identify the root cause.
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## The 4-Checkpoint Pre-Send Evaluation
Gmail and Outlook run 4 invisible checkpoints BEFORE your email reaches the inbox. If you fail any of them, your prospect never sees a thing. A vast majority of deliverability problems trace back to one of these four checkpoints.
### Checkpoint 1: Authentication
**What it checks:** Are your SPF, DKIM, and DMARC records properly configured?
**What happens when it fails:** Your email is flagged as potentially spoofed. It either goes to spam or gets silently dropped.
**How to diagnose:** Use mail-tester.com or MXToolbox to verify DNS records. Send a test email and check the headers for SPF pass/fail, DKIM pass/fail, and DMARC alignment.
**Common failures:**
- Multiple SPF records on the same domain (only one is allowed).
- DKIM not enabled through the email provider.
- DMARC not set up at all.
- DNS records pointing to the wrong server after a provider migration.
### Checkpoint 2: Trust Scoring
**What it checks:** Does your sending domain and IP have a positive reputation?
**What happens when it fails:** Your emails get deprioritised or routed to spam. High trust = Primary tab. Low trust = spam folder.
**How to diagnose:** Check domain age (newly registered domains have zero trust). Check if the domain has been used for spam previously (Google Postmaster Tools, Talos Intelligence). Check warmup history.
**Common failures:**
- Brand-new domain with zero sending history jumping straight to 100+ emails per day.
- Buying expired domains that have spam history attached to them.
- Skipping warmup entirely.
- Previous owner of the domain had a bad sending reputation.
### Checkpoint 3: Behavioural Analysis
**What it checks:** Does your sending pattern look like a real human or a mass mailer?
**What happens when it fails:** Silent throttling. Your emails still technically "send" but providers slow, stagger, or quietly deprioritise your delivery. Your pipeline shrinks and you have no idea why.
**How to diagnose:** Check sending velocity (how many emails per hour). Check bounce rate (should be below 1.5%). Check reply rate (healthy cold email reply rates sit between 3-8%). Check if you're seeing declining open rates over time with no other changes.
**Common failures:**
- Sending 50+ emails from a single inbox in one hour.
- Bounce rate above 2% (list hygiene problem).
- Reply rate below 1% over a sustained period (signals to providers that nobody wants your emails).
- Irregular sending patterns (nothing for 3 days, then 200 emails in one day).
### Checkpoint 4: Identity Validation
**What it checks:** Does this sender look like a real person with real sending history?
**What happens when it fails:** Providers flag the sender as likely automated or fake. Especially aggressive against freshly created inboxes with no history.
**How to diagnose:** Check if the inbox has a profile photo, display name, email signature. Check if the inbox has non-cold-email activity (newsletter signups, account registrations, normal email conversations). Check inbox age.
**Common failures:**
- Inbox created yesterday, 100 cold emails sent today.
- No profile photo, no display name, no signature.
- Zero non-outreach email activity (the inbox only sends cold email and nothing else).
- Generic display names like "Sales Team" instead of a real person's name.
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## Silent Throttling
### What It Is
Silent throttling is when email providers deliberately slow, stagger, or quietly deprioritise your sends to protect inboxes from suspicious behaviour. Unlike a hard bounce or spam folder placement, throttling gives you almost no visible signal that something is wrong.
### How to Detect It
- Gradually declining open rates over 2-3 weeks with no changes to your copy or lists.
- Emails showing as "delivered" in your sequencer but reply rates dropping steadily.
- Increasing delay between send time and first open (emails sitting unread longer than usual).
- Some emails never getting opened at all despite historically strong engagement.
### What Triggers Throttling
- Sending velocity that exceeds provider expectations for your inbox's reputation level.
- Bounce rate climbing above 1.5%.
- Low reply rates sustained over multiple weeks.
- Sudden volume increases (going from 10 emails/day to 50 emails/day overnight).
- Multiple spam complaints from recipients.
### How to Recover
1. Reduce sending volume to 50% of current levels immediately.
2. Pause any inbox that's been active for less than 3 weeks.
3. Re-verify your email list. Remove anyone who hasn't engaged in 60+ days.
4. Run warmup on affected inboxes for 7-14 days before resuming.
5. Ramp back up slowly. Add 2-3 emails per day per inbox per week.
6. Monitor bounce rates daily during recovery. If bounces exceed 1.5%, pause again.
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## The 6 Industry Mistakes (Diagnostic Checklist)
When diagnosing deliverability problems, check for these 6 common mistakes first. They account for the vast majority of issues across 2,000+ customers.
### Mistake 1: Skipping DNS Configuration
- SPF, DKIM, DMARC not set up or misconfigured.
- Fix: configure all three DNS records before sending a single email.
- Check: mail-tester.com score should be 9/10 or higher.
### Mistake 2: Sending from Primary Domain
- Cold email sent from the main business domain instead of lookalike domains.
- Fix: buy dedicated outreach domains. Keep primary domain completely clean.
- Check: is the sending domain the same as the company website? If yes, that's the problem.
### Mistake 3: Skipping Warmup
- New inboxes jumping straight to cold outreach with zero sending history.
- Fix: 14+ days of warmup before any cold outreach.
- Check: how old is the inbox? How many days of warmup before first cold send?
### Mistake 4: Single Provider Dependency
- 100% Google or 100% Outlook. No diversification.
- Fix: Two-Lane Provider Strategy. 70/30 or 50/50 split between Google and Outlook.
- Check: how many providers are they using? If only one, they're exposed.
### Mistake 5: Overpaying for Infrastructure
- Paying $6/inbox when $3.50 exists. Usually middlemen adding zero technical value.
- Fix: find resellers who handle the technical setup at fair prices.
- Check: what are they paying per inbox? How does it compare to market rate?
### Mistake 6: "Just Bumping This" Follow-Ups
- Follow-up emails that add zero value. Just "checking in" or "bumping this to the top."
- Fix: every follow-up adds something new. A case study, an insight, a different angle.
- Check: read their follow-up emails. Does each one add new information?
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## Provider-Specific Troubleshooting
### Google Workspace Issues
- **Emails going to Promotions tab:** Usually a content issue. Remove HTML, images, and links from the first email. Plain text performs better for cold outreach.
- **Sudden spike in bounces:** Check if Google has flagged the sending domain. Use Google Postmaster Tools to see domain reputation.
- **Account suspended:** Google TOS violation. Usually from exceeding sending limits or recipient complaints. Need to appeal and may need new infrastructure.
### Outlook/Microsoft Issues
- **Emails going to Junk/Clutter:** Microsoft's filtering is more aggressive than Google's. Ensure DKIM signing is active. Reduce sending volume from Outlook inboxes.
- **SmartScreen filtering:** Microsoft runs additional content scanning. Avoid trigger phrases ("free", "act now", "limited time") in subject lines and body copy.
- **Deliverability inconsistency:** Outlook deliverability can vary by recipient organisation's security settings. Some companies have aggressive inbound filters that override sender reputation.
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## Diagnostic Decision Tree
### "My emails are landing in spam"
1. Check DNS authentication (Checkpoint 1). If SPF/DKIM/DMARC fail, fix that first.
2. If authentication is clean, check domain/IP reputation (Checkpoint 2). Use Google Postmaster Tools and Talos Intelligence.
3. If reputation is clean, check sending patterns (Checkpoint 3). Are you sending too many too fast? Is bounce rate above 1.5%?
4. If patterns look normal, check identity signals (Checkpoint 4). Profile photo, display name, signature, inbox age, non-outreach activity.
5. If all 4 checkpoints pass, the issue is likely content-based. Check for spam trigger words, excessive links, or HTML formatting.
### "My reply rate dropped suddenly"
1. Check if anything changed in your infrastructure (new domains, new provider, DNS change).
2. Check for silent throttling signals (declining open rates over 2-3 weeks).
3. Check list quality. Did you upload a new list? What's the bounce rate on recent sends?
4. Check if a competitor or similar sender got flagged, which can affect shared IP reputation.
5. If infrastructure is clean, the issue is likely targeting or copy, not deliverability.
### "My bounce rate is climbing"
1. Check list hygiene. When was the list last verified? Are you using an email verification tool?
2. Target bounce rate: below 1.5%. Above 2% is a red flag. Above 5% means pause sending immediately.
3. Verify the email addresses before uploading to your sequencer. Tools like NeverBounce, ZeroBounce, or MillionVerifier.
4. Remove any address that has bounced. Do not retry bounced addresses.
5. If using scraped lists, verification is non-negotiable before any send.