google app engine - Sender address rejected: Domain not found -

google app engine - Sender address rejected: Domain not found -

i'm getting error below when sending mail service via smtp through google apps mail. can see why error? far can tell domain exists!

this warning message only. not need resend message. delivery next recipient has been delayed: a.kozikowski@tutek.pl message retried 2 more day(s) technical details of temporary failure: google tried deliver message, rejected server recipient domain tutek.pl mx.maxus.pl. [213.241.89.166]. error other server returned was: 450 4.1.8 <aquarius@aquariusprams.co.uk>: sender address rejected: domain not found

this error means recipient mail service server can not resolve mx (and a) records of aquariusprams.co.uk. works fine here, generic dns problem on recipient side or routing issue between recipient , nameservers ns1.console-covers.com / ns2.console-covers.com.

google-app-engine email smtp gmail