220 MAILSVR.ZTCOGROUP.LOCAL Microsoft ESMTP MAIL Service ready at Sun, 9 Mar 2014 13:39:02+0400 [811 ms]
EHLO MXTB-PWS3.mxtoolbox.com
250-MAILSVR.ZTCOGROUP.LOCAL Hello [64.20.227.133]
250-SIZE 37748736
250-PIPELINING
250-DSN
250-ENHANCEDSTATUSCODES
250-STARTTLS
250-X-ANONYMOUSTLS
250-AUTH NTLM
250-X-EXPS GSSAPI NTLM
250-8BITMIME
250-BINARYMIME
250-CHUNKING
250 XRDST [874 ms]
MAIL FROM: <supertool@mxtoolbox.com>
250 2.1.0 Sender OK [874 ms]
RCPT TO: <test@example.com>
550 5.7.1 Unable to relay [5881 ms]
Mails with Signature image are bounced we found the above info from MXtoolbox how to fix this please help.