I’m having trouble with some emails getting bounced back when using Mailgun for sending. I keep running into two main error types that are blocking my email delivery.
The first error says something about mailbox unavailable and DNS MX record issues (error 550). The second one tells me the domain in the From field is not valid.
I’m not sure if these problems are happening because of something wrong with my setup or if it’s an issue on the recipient’s side. What steps should I take to troubleshoot and resolve these delivery problems? Any advice on how to properly configure the domain settings would be really helpful.
Delivery failures suck but they’re fixable with the right setup.
550 MX errors mean the recipient’s server can’t find your domain’s MX records. Check your DNS config and make sure it’s propagated.
Invalid domain errors in the From field? Your authentication’s broken - usually SPF, DKIM, or DMARC problems.
Skip the manual troubleshooting. Build an automated system that watches your email delivery and catches issues before they blow up.
I’ve got automation that checks domain health, validates DNS records, and retries failed sends with different configs. When stuff bounces, it logs the error codes and switches to backup methods.
You can automate the whole troubleshooting mess - workflows that test SPF records, verify DKIM signatures, and monitor sender reputation without you lifting a finger.
Let automation handle the monitoring and give you reports on what’s broken. Set up daily domain validation checks that run themselves.
Saves me hours every week and catches problems before they kill important emails.
Had the same Mailgun headaches last year - turned out to be DNS issues on my side, not the recipients. For those 550 MX errors, double-check your sending domain’s MX records. That’s usually what gets missed during setup. The invalid domain error? Your SPF record is probably missing or messed up. Add “include:mailgun.org” to your TXT record to fix that. Make sure DKIM is set up right through Mailgun’s domain verification too. Their domain verification tool saved me - use it to check all your DNS records propagated correctly. DNS changes can take up to 48 hours to spread everywhere, so be patient. Watch your delivery logs for a few days after making changes to make sure everything’s working.
Your bounce issues are killing your deliverability. Stop manually checking DNS records every time something breaks - you need automated monitoring.
I built a workflow that constantly checks all my email infrastructure. It validates MX records, tests SPF and DKIM, and monitors sender reputation across ISPs.
When bounces happen, automation sorts them by error type and triggers responses. Hard bounces? Addresses get removed immediately. Soft bounces? They’re queued for retry with exponential backoff.
The real win is predictive monitoring. My system catches DNS propagation delays before they cause failures. It also rotates between Mailgun IP pools when reputation tanks.
For your specific errors, automate the fixes. Build flows that detect 550 MX errors and verify DNS setup against multiple resolvers. When domain validation fails, cross-check SPF records and get alerts showing exactly what’s broken.
This saved me last month when DNS changes broke authentication. Automation caught it in minutes and switched to backup domain while I fixed records.
check your mailgun sender reputation first - if it’s tanked, emails will bounce no matter how perfect your dns is. those 550 errors could be recipient servers blocking you, not mx problems. try test emails from a different ip range in mailgun to see if that’s what’s causing it. also make sure your from address matches exactly what you set up during domain verification.
These delivery issues are usually DNS problems, not bad recipient addresses. Run a dig command on your domain - check if your MX records are actually resolving. Sometimes DNS providers show records as ‘added’ but they’re not propagating. For the invalid domain error, make sure your From address domain matches exactly what you verified in Mailgun. Subdomains need separate verification. I’ve seen people use ‘[email protected]’ but only verify ‘example.com’ - that won’t work. Try Mailgun’s email validation API on problematic addresses before sending. It catches undeliverable ones that cause 550 bounces and helps you tell DNS issues from actually invalid addresses. Also check if your sending volume jumped recently. ISPs flag domains that go from low to high volume without warming up first.