We had the same problem: ip1/banner1, ip2/banner1 - correct ip1/banner1, ip2/banner2
System: Plesk 10.4.4, CentOS 6, 64 bit
http://www.linuxmail.info/postfix-multiple-ip-address-smtp-greeting/
Plesk overwrites the master.cf.
To prevent Plesk from overwriting: chattr +i /etc/postfix/master.cf
Shell: service postfix restart
This worked for us.
CU
hologer