When to Run This Audit
Reply rates dropped. Open rates are crashing. Bounces are spiking. Something changed — and the longer you wait to diagnose, the more damage compounds.
This audit template is what a deliverability specialist would walk through to identify what broke. It's structured so you can run it top-to-bottom in 30 minutes and land on a root cause.
The order matters. Each section rules out a category of failures before you move on. Don't skip ahead — the cheapest fixes are usually in the first three sections, and skipping them means you'll spend hours debugging the wrong thing.
Step 1: Confirm the Scope (5 minutes)
Which mailboxes are affected? All of them, or a subset? If it's a subset, what do they have in common — same domain? Same warmup batch? Same campaign?
Which recipients are affected? Gmail recipients specifically? Outlook/Microsoft? Corporate domains? A single-provider drop is a provider-specific reputation problem. A universal drop is an infrastructure or content problem.
When did it start? Exact timestamp if possible. Correlate with anything that changed — new campaigns launched, volume increases, domain additions, content changes.
Is it a metrics issue or a real issue? Check actual inbox placement with a seed test (mail-tester, Glock Apps). Don't trust your sending tool's metrics — they can lag or misreport.
Step 2: Authentication Check (5 minutes)
Run an SPF/DKIM/DMARC check on every affected sending domain. MXToolbox Domain Health gives this in one scan.
SPF pass required. v=spf1 include:your-sender ~all. Only one SPF record. If you added a new sending platform recently, SPF may have broken.
DKIM signing check. Send a test email to yourself from each affected mailbox. View headers — look for DKIM-Signature and Authentication-Results: dkim=pass. If dkim=fail or dkim=none, the key isn't published or the record is corrupted.
DMARC alignment. Authentication-Results: dmarc=pass. Failure here usually means SPF or DKIM alignment issues — the envelope-from or signing domain doesn't match the visible from domain.
Reverse DNS. Your sending IP's PTR should resolve to a hostname on your sending domain. Missing PTR is a common cause of Outlook/Microsoft spam folder issues.
Step 3: Reputation Check (10 minutes)
Google Postmaster Tools. Check domain reputation (High / Medium / Low / Bad). IP reputation. Spam rate. Authentication pass rates. Any drop here = Gmail is the problem.
Microsoft SNDS. Check IP status (Green / Yellow / Red). Filter result percentage. If Red, you're essentially not delivering to Microsoft. If Yellow, partial delivery.
Blacklist status. MXToolbox Blacklist Check on every sending IP and domain. Cross-reference with Spamhaus, Barracuda, SORBS, SpamCop. Any hit = immediate deliverability cliff.
Domain reputation services. Talos Intelligence (Cisco), Barracuda Central, Sender Score. Low scores indicate broader reputation damage.
If reputation is bad at a specific provider: Don't keep sending. Volume at a degraded reputation just deepens the hole. Pause that provider's sends, fix the root cause, warm back up.
Step 4: Content Audit (5 minutes)
Run each email template through mail-tester.com. Any score below 9.0 has content issues. The report itemizes what's flagged.
Subject line review. Spam trigger words (free, guaranteed, click here, winner, urgent, act now). Excessive caps or punctuation. Non-ASCII characters and emoji.
Link density. Cold emails should have 0–1 links. More than 2 is a red flag. Every link should be to a reputable domain (your domain, not a shortener).
Image-to-text ratio. Cold email should be 90%+ plain text. Heavy HTML or image-heavy emails trigger content filters.
Personalization tokens rendering correctly. Hi [First Name] with an unrendered token is an instant spam signal. Check a live send, not just a preview.
Unsubscribe link. Required by CAN-SPAM. Also required for good deliverability — visible, clickable unsubscribe improves sender reputation.
Step 5: Volume and Pattern Audit (5 minutes)
Per-mailbox daily volume. Should be 20–30 sends/day maximum. Higher volume per mailbox hits provider-specific rate limits and triggers automated flagging.
Per-domain daily volume. Total across all mailboxes on a domain. If you suddenly doubled volume on a single domain, that alone can cause a reputation drop.
Warmup-to-real ratio. New mailboxes should maintain 50/50 warmup-to-real sends for the first 2 weeks, then gradually shift. If you ramped real sends too fast, that's likely the cause.
Time-of-day patterns. Sudden shifts to sending at unusual hours (3am local time, for example) look like automated spam operations.
Recipient domain concentration. Sending 80% of volume to Gmail addresses can trigger Gmail-specific filtering. Mix recipient domains when possible.
Step 6: List Quality Audit (5 minutes)
Bounce rate last 7 days. Over 5% = list quality problem. Over 10% = immediate pause. Hard bounces are the clearest signal of list decay.
Complaint rate last 7 days. Over 0.1% = warning. Over 0.3% = you're headed for blacklisting. Pause all sends until you fix the targeting or content causing complaints.
Re-verify recent lists. Any list imported more than 30 days ago should be re-verified. Use ZeroBounce or equivalent.
Check for spam traps. Paid verification services flag known traps. One trap hit can explain a sudden deliverability cliff.
Suppression list integrity. Confirm unsubscribes, bounces, and past complaints are actually being filtered from new campaigns. Broken suppression = recurring complaints = blacklisting.
How to Use the Audit Results
Single-provider issue (only Gmail drop, for example). Fix with provider-specific action: reduce volume to that provider, warm back up, check Postmaster Tools daily until reputation recovers.
Authentication failure. Fix the DNS record immediately. Authentication issues compound fast — every failed send deepens the reputation damage.
Blacklist listing. Identify which list, fix the root cause, request delisting. Pause sending from affected IPs/domains until delisted.
Content issue. Rewrite the flagged elements. Re-test. Don't resume until mail-tester scores above 9.0 consistently.
Volume/pattern issue. Dial volume back to 50% for 1 week. Resume ramp only after reputation recovers.
List issue. Stop sending. Re-verify every active list. Resume only after cleaning.
Can't identify the cause? Schedule a 30-minute call with a deliverability specialist. ColdRelay customers get this included — non-customers can book through MXToolbox or Email on Acid.
Frequently Asked Questions
How quickly should I run this audit after noticing a drop?
Within 24 hours. Deliverability problems compound — every day of degraded sending makes the reputation damage worse. Most recoverable issues stay recoverable for 3–5 days; beyond that, rebuilding infrastructure is often faster than fixing.
What if the audit doesn't find a cause?
Either the issue is at the ESP/infrastructure level (something changed at Google, Microsoft, or your provider), or it's a very recent blacklisting that hasn't propagated to detection tools yet. Pause sending for 48 hours and re-run the audit — often the cause becomes visible as reputation data updates.
Can I run this audit preemptively?
Yes, and you should. Monthly preemptive audits catch drift before it becomes a crisis. The DNS, reputation, and content sections take 15 minutes and prevent most emergencies.
How does ColdRelay handle this?
ColdRelay runs continuous equivalents of steps 2, 3, and 5 automatically — authentication verification, reputation monitoring, and volume/pattern analysis. Alerts fire before problems affect deliverability. Steps 4 and 6 (content and list quality) remain your responsibility but ColdRelay provides the tools.