DNS error 421 DNS temporary failure

[cpaun]

I have the new ispconfig , 2.2.26 and host in 6 domains.
All domain it is configure on same mod , email it is working fine on webmail in and out. The problem come when I configure outlook on client site for domain1 it is ok but for domain2 I get:

Send test e-mail message: Cannot send the message. Verify the e-mail address in your account properties. The server responded: 421 DNS temporary failure at return MX check, try again later (#4.3.0)

On both account I use same SMTP ( from ISP)
Anybody have any ideea what can be?

[falko]

What's in the mail log when this happens?