Issue
Users attempting to register through a portal application are not receiving automated verification emails when using certain email providers or corporate domains.
The issue may initially impact:
Hotmail/Outlook addresses
Microsoft 365 corporate domains
Other external email providers
Business Impact:
Users cannot complete onboarding or account registration because verification emails are not received.
Symptoms
Verification email not received after registration
No visible application errors during signup
Some email providers succeed while others fail
Delivery failures occur silently without alerting
Example reproduction:
Navigate to the portal signup page
Select "Sign Up"
Register using a Hotmail or corporate email address
Verification email is not received
Investigation Findings
Initial Validation
Testing may show:
Internal/test domains → Success
Gmail → Success (initially)
Hotmail/Outlook → Failure
Corporate domains → Failure
Key Checks
Compare lower and production environment email behaviour
Reviewe SPF/DKIM/DMARC validation
Reviewe email provider configuration
Check External Email Domain configuration
Review recipient-side rejection behaviour
Validate DNS records
Review bounce/suppression logs
Example of Error
Recipient-side rejection indicating authentication failure:
5.7.515 Access denied, sending domain doesn't meet the required authentication level
Authentication status may show:
SPF = Pass
DKIM = Fail
DMARC = Pass
Root Cause Indicators
Investigation may identify:
Missing or invalid DKIM DNS records
External Email Domain configuration misalignment
Corrupted or outdated domain verification configuration
Email providers enforcing stricter authentication validation
Different email providers may enforce authentication policies differently, causing staggered impact across domains.
Resolution
The issue can typically be resolved by:
Recreating the External Email Domain configuration
Regenerating DNS and DKIM records
Updating DNS records
Re-establishing domain verification
Validating successful email delivery across affected domains
Result:
Email delivery resumes successfully across impacted email providers.
Troubleshooting Steps
Step 1: Validate Email Behaviour
Test signup flow using:
Hotmail/Outlook account
Corporate domain
Gmail account
Document which domains fail.
Step 2: Check Authentication Status
Validate:
SPF
DKIM
DMARC
Useful tools:
MXToolbox
DNS verification tools
Email provider verification utilities
Step 3: Review External Email Domain Configuration
Within the FENX application:
Open External Email Domain configuration
Verify DKIM entries exist
Confirm domain verification status
Check whether the configuration is enabled
Step 4: Review Recipient Rejections
Check logs for:
550 errors
5.7.x authentication failures
Microsoft rejection responses
Bounce/suppression events
Step 5: Recreate External Email Domain
If configuration corruption or DNS mismatch is suspected:
Delete existing External Email Domain
Recreate configuration
Generate new DNS/DKIM records
Update DNS records
Re-verify domain
Retest delivery
Preventive Recommendations
Monitor External Email Domain verification status regularly
Implement alerting for delivery failures and suppression spikes
Validate DKIM records after DNS changes
Periodically test onboarding email delivery across multiple email providers