Postfix to relay mails to other SMTP for particular domain

Have an SMTP server setup running in postfix, only for sending mails . Now the requirement is i want to relay mails for particular domain to end user through other SMTP , without disturbing default setup (i.e, without relaying)

Existing Setup

   Application -->  My SMTP  ---> End user

Required for particular domain to send mails

 Application ( [email protected] ) --> My SMTP  --> SMTP of XYZ.com

If you want to send to a server other than what say the MX records in DNS for a domain, you can add a line in /etc/postfix/transport:

abc.com        smtp:mail.xyz.com

Then run postmap /etc/postfix/transport.

If it isn't already, add transport_maps = hash:/etc/postfix/transport to /etc/postfix/main.cf and run postfix reload.