Spam Diagnostic Checklist
Five checks, in the order worth doing them. Authentication first, because it is the most common cause and the easiest to confirm, then your reputation, the content itself, the state of your list and how you send. The last section lists what each of the big providers reacts to.
Step 1: Authentication
| Check |
How |
Pass Criteria |
| SPF |
Sender Domains > click domain > check SPF status |
Shows Success (green) |
| DKIM |
Sender Domains > click domain > check DKIM status |
Shows Success (green) |
| DMARC |
Sender Domains > click domain > check DMARC status |
Shows Success (green) |
| DMARC alignment |
DMARC policy aligns with SPF and DKIM domains |
p=none minimum, p=quarantine or p=reject recommended |
Step 2: Sender Reputation
| Check |
How |
Red Flag |
| Complaint rate |
Delivery Events > filter Complained > calculate rate |
Above 0.1% (1 per 1,000 emails) |
| Bounce rate |
Delivery Events > filter HardBounced > calculate rate |
Above 2% |
| Blocklist status |
Check MxToolbox.com or similar |
Any active listing |
| Google Postmaster Tools |
Set up at postmaster.google.com |
Domain reputation "Low" or "Bad" |
Step 3: Email Content
| Check |
Fix |
| No unsubscribe link |
Add {EEUnsubscribeLink} to email body |
| No plain text version |
Add plain text version in Email Content editor |
| High image-to-text ratio |
Add more text content, reduce images |
| Spam trigger words |
Remove "free", "act now", "limited time", "winner", "congratulations" |
| ALL CAPS in subject/body |
Use normal capitalization |
| Excessive exclamation marks |
Limit to one per sentence maximum |
| Shortened URLs |
Use full destination URLs |
| No physical address |
Include company address (required by CAN-SPAM) |
Step 4: List Hygiene
| Check |
Fix |
| Stale list (no engagement in 90+ days) |
Create a Segment for engaged contacts only |
| High hard bounce rate |
Suppress hard-bounced addresses via Suppression Lists |
| Purchased or scraped list |
Never send to purchased lists — they contain spam traps |
| No double opt-in |
Implement confirmation for new signups via Pages & Forms |
Step 5: Sending Practices
| Check |
Fix |
| New domain, high volume |
Use Warm-up schedule in Schedule to gradually increase |
| No Volume Caps |
Set Volume Caps on Send Integration to control hourly/daily rate |
| Inconsistent sending |
Send on a regular schedule — erratic patterns look suspicious |
| Sending to inactive contacts |
Segment by last engagement date, exclude 90+ day inactive |
Common Spam Filter Triggers by Provider
Gmail
- Checks engagement (opens/clicks) heavily — low engagement = more spam
- Google Postmaster Tools shows domain/IP reputation
- DMARC alignment is strictly enforced
Microsoft (Outlook/Hotmail)
- Smart Network Data Services (SNDS) shows IP reputation
- Strict on content — avoid "salesy" language
- Check junkmail@office365.microsoft.com for false positive reports
Yahoo/AOL
- Complaint feedback loops — high complaint rates = immediate blocking
- Check Sender Hub (previously CFL) at senders.yahooinc.com
