What we check
We check if your MX records have incorrect priority values
We check if your MX records have incorrect priority values that could cause email routing problems. Wrong MX priority can route emails through backup servers not configured to handle production traffic, causing delays, lost messages, or routing loops.
Security Impact
Why MX priority configuration matters
Delayed email delivery
Wrong priority values can route emails through backup servers that aren't optimized for high volume, causing significant delivery delays.
Lost messages
Backup servers may not be configured correctly, lack spam filtering, or have storage limits. Emails routed incorrectly can be rejected or dropped.
Routing loops
Misconfigured priorities can create mail loops where emails bounce between servers indefinitely until timing out.
Inconsistent spam filtering
If emails randomly route through different servers with different spam configurations, some legitimate emails may be filtered while spam gets through.
Implementation
How to fix MX priority issues
With Httpeace
Httpeace automatically detects MX priority misconfigurations:
- Add your domain to Httpeace
- We check MX priority values automatically every day
- Get instant alerts when priority issues are detected
- See recommended priority configuration in your dashboard
Without Httpeace
Manual MX priority management requires understanding routing logic:
# Check MX records and priorities dig MX yourdomain.com +short # Verify priority ordering nslookup -type=MX yourdomain.com # Test mail server response telnet mail.example.com 25 # Check routing behavior # Send test emails and trace delivery path
You'll need to:
- Understand MX priority logic (lower numbers = higher priority)
- Check current MX records with dig or nslookup
- Identify which server should be primary vs backup
- Verify backup servers are configured to handle mail
- Update priority values to match intended routing
- Use incremental priorities (10, 20, 30) for clarity
- Avoid equal priorities unless doing deliberate load balancing
- Test mail delivery to verify correct routing
- Send emails and check which server receives them
- Simulate primary server failure to test backup routing
- Coordinate with email provider on recommended priorities
- Document intended mail routing for team reference
- Monitor MX records daily for accidental changes
- Set up alerts if priority configuration changes unexpectedly
- Update priorities when adding or removing mail servers
MX priority misconfiguration is subtle but dangerous. Wrong priorities route emails through servers that aren't prepared to handle production traffic, causing delays, lost messages, or complete delivery failure.
FAQ
Frequently asked questions
What is MX priority?
MX priority determines which mail server to try first when delivering email. Lower numbers = higher priority. Sending servers try the lowest priority first, then fall back to higher numbers if the first server is unavailable.
Should all MX records have different priorities?
Usually yes, unless you have multiple servers configured for load balancing. Equal priorities cause random selection, which is only appropriate when all servers are identical and can handle production traffic.
Can I use priority 0?
Yes, priority 0 is valid and has the highest precedence. Some providers like Microsoft 365 use priority 0 for their mail servers. However, 10 is more common for primary servers.
What happens if my primary server is down?
Sending servers automatically try the next priority level (your backup server). Emails queue at the sender until your primary server recovers or the backup accepts delivery. This is why having backup MX records is important.
How does Httpeace check MX priorities?
We analyze your MX records daily, checking for common priority misconfigurations like equal priorities without load balancing, backup servers set as primary, or unusual priority patterns that could cause routing issues.
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