DNS problems causing email delays to mail.mil

Having trouble sending mail to mail.mil? You're not alone. One of their three authoritative DNS servers (sdns3.csd.disa.mil) for the domain mail.mil appears to be unreachable right now. Confirm for yourself here.

If you use public DNS, results are mixed. My testing shows that Cloudflare can find the MX record; Google Public DNS cannot.

If you're lucky enough where it's easy to hard code an MX setting in your mail sending infrastructure, you could probably get away with temporarily directly mapping mail destined to mail.mil so that your MTAs just directly connect to IPs -, as they seem to be responding just fine on port 25. (Those IPs are just a few of the mail servers that host mail for that domain.) Of course, that's not a scalable long-term solution.

November 1, 2021 Update: Things appear to be resolved; DNS for mail.mil seems to be responding quickly and reliably.



  1. Is this still happening today 10/29? Folks at our company are still seeing this issue today and I'm trying to make sure it is nothing on our end.

  2. Any word if this is still occurring as of today? It appears as though our SMTP Security vendor is having issues reaching the DNS server. Email to .MIL domains delivers successfully about 1/20.

  3. Yeah, I think it's still happening now.


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