Mail flow broken in my lab

I have a exchange 2013 lab. Internal and external mail flow were there but now suddenly it's not working. When I try to do internal relay it through me error "451 4.7.0 Temporary server error. Please try again later. PRX4"

Note: License got expired. Will it affect eventhe internal mail flow???

220 EXUM13.lyncnet.net Microsoft ESMTP MAIL Service ready at Fri, 26 Sep 2014 11
:43:21 -0600
ehlo lyncnet.net
250-EXUM13.lyncnet.net Hello [fe80::9044:afda:cf11:30ee%14]
250-SIZE 36700160
250-PIPELINING
250-DSN
250-ENHANCEDSTATUSCODES
250-STARTTLS
250-X-ANONYMOUSTLS
250-AUTH
250-X-EXPS GSSAPI NTLM
250-8BITMIME
250-BINARYMIME
250-CHUNKING
250 XRDST
mail from: siva@lyncnet.net
250 2.1.0 Sender OK
rcpt to: siva@lyncnet.net
250 2.1.5 Recipient OK
data
354 Start mail input; end with <CRLF>.<CRLF>
test mail from sivakumar
.
451 4.7.0 Temporary server error. Please try again later. PRX4

Please help!

Thanks

Funnyghost