Reporting-MTA: dns;
Action: failed
Final-Recipient: rfc822
Status: 5.0.0
Remote-MTA: dns;
Diagnostic-Code: smtp; 552 5.3.4 Message size exceeds fixed limit
postconf | grep message_size_limit
message_size_limit = 10240000 #This is default message size
echo "message_size_limit = 30480000" >> /etc/postfix/main.cf
service postfix reload