Separate Destination domain and Relay Zimbra

** We can relay full server from one server to another server

vi /etc/postfix/main.cf
relayhost = [smtpgw.tayabkhan.com]:587
or
relayhost = [smtpgw.tayabkhan.com]:25

** We can separate a destination domains mail via another SMTP server.

** check tranport_maps are in main.cf
vi /etc/postfix/main.cf

 transport_maps = hash:/etc/postfix/transport

** Login Mail server  and  vi /etc/postfix/transport
hotmail.com             :[smtpgw.tayabkhan.com]

-----------------------------------------
*** Loging to smtpgw(smtpgw.tayabkhan.com) server: and allow IP of mail server in MyNetworks

** if postfix then goto vi /etc/postfix/main.cf and add server ip to mynetworks
mynetworks =  127.0.0.0/8, 192.168.10.0/24

** if Zimbra then,
root@mail# su - zimbra
[zimbra@smtpgw2 ~]$ postconf mynetworks

***Outpur will be like bellow...........
mynetworks = 127.0.0.0/8 192.168.1.0/24 [::1]/128 [fe80::]/64

*** Add your mx server IP 10.10.10.200 by bellow command
[zimbra@smtpgw2 ~]$  zmprov ms smtpgw2.tayabkhan.com zimbraMtaMyNetworks '127.0.0.0/8 192.168.1.0/24 10.10.10.200/32 [::1]/128 [fe80::]/64'

[zimbra@smtpgw2 ~]$  postfix reload