Who This Is For / When to Use
Use this article if you want to:
Understand why emails are bouncing
Monitor delivery and bounce rates
Identify sender reputation or domain issues
Fix problems preventing emails from reaching inboxes
Learn what specific bounce codes mean
Access Email Analytics and Bounce Classification
Go to Settings.
Select Email Services.
Open the Bounce Classification tab.
Email Analytics Overview
What Email Analytics Shows
Email Analytics provides high-level delivery performance metrics, including:
Total emails delivered
Delivery rate
Bounce rate
ESP or IP blocks
Date-based performance trends
These metrics help you assess overall email health.
Bounce Classification Overview
What Bounce Classification Is
Bounce Classification categorizes failed email deliveries and explains:
Why an email bounced
Where it was rejected (recipient server, provider, or internal system)
What action to take to prevent future failures
Why Bounce Classification Matters
Protects sender reputation
Prevents repeated delivery failures
Improves inbox placement
Automatically suppresses harmful sends
Hard Bounces vs Soft Bounces
Hard Bounce
A permanent failure.
Examples:
Invalid email address
Domain does not exist
Recipient address permanently rejected
System Behavior:
Hard-bounced emails are automatically suppressed and cannot be emailed again.
Soft Bounce
A temporary failure.
Examples:
Mailbox full
Temporary server issue
Rate limiting by provider
System Behavior:
Soft bounces may be retried automatically.
Bounce Codes and Definitions
The information below explains common bounce categories you may see in Kyrios.
Mailbox Full
Error Codes: 452, 552
Meaning: Recipient inbox is full and cannot accept new emails
Action: Retry later or contact recipient
Invalid Address
Error Codes: 550, 5.1.1
Meaning: Email address does not exist or is incorrectly formatted
Action: Correct or remove the email address
DMARC Failure
Error Codes: 550
Meaning: Email failed DMARC authentication checks
Action:
Ensure SPF and DKIM are correctly configured
Verify sending domain alignment
Sender Reputation
Error Codes: 550, 5.7.1
Meaning: Emails blocked due to poor domain or IP reputation
Action:
Reduce sending volume
Verify sender emails
Use a dedicated sending domain
ESP / IP Block
Meaning: Email provider blocked the sending IP or domain
Action:
Review bounce details
Improve sending practices
Contact support if persistent
User Reported Spam
Meaning: Recipient marked the email as spam
Action:
Review content relevance
Reduce frequency
Ensure opt-in compliance
Internal Retry Exhausted
Error Codes: 602
Meaning: System attempted delivery multiple times without success
Action: Investigate recipient server or domain issues
Using Filters and Drilldowns
You can filter bounce data by:
Date range
Sending domain
Email type
Provider or error category
This helps isolate the root cause of delivery problems.
Automatic Suppression Behavior
What Gets Suppressed
Hard-bounced email addresses
Repeated invalid addresses
Addresses flagged as harmful to sender reputation
Why Suppression Happens
Suppression protects:
Your sending domain
Your IP reputation
Overall deliverability
Suppressed emails cannot be re-sent unless corrected and revalidated.
Common Deliverability Issues and Fixes
High Bounce Rate
Likely Causes:
Poor list quality
Unverified sender email
No dedicated sending domain
Fix: Clean your list and verify sender emails.
Emails Blocked by Gmail or Outlook
Likely Cause: Sender reputation issue
Fix: Reduce volume, improve authentication, and monitor bounce feedback.
Delivery Rate Suddenly Drops
Likely Cause: Recent content or sending change
Fix: Review recent campaigns and bounce classifications.
Best Practices for Deliverability
Use a dedicated sending domain
Verify sender email addresses
Avoid purchased or scraped lists
Monitor bounce classifications regularly
Act on DMARC and reputation warnings quickly
What to Do Next
If you’re troubleshooting delivery issues:
Review bounce classifications
Fix the root cause
Monitor analytics over time