Multiple IPs for postfix

[Cristiano]

Hi Guys

I´m writing here because I could not find a solution on a google
search.
I have a mail server and we have 4 usable Ips on this server.

Postfix is configured and working for a very long time.
I already configured postfix to have different greetings to different
IP addresses:

Here is whats on my master.conf:

localhost:smtp inet n - n - -
smtpd
<IP1>:smtp inet n - n - - smtpd
<IP2>:smtp inet n - n - - smtpd -o
myhostname=mail1.host.com
<IP3>:smtp inet n - n - - smtpd -o
myhostname=mail2.host.com
<IP4>:smtp inet n - n - - smtpd -o
myhostname=mail3.host.com

This is working 100% fine. According to the IP that the connection is
coming from, a different greeting is used.

My question is regarding the options to send emails using different IP
addresses.

I would like to use one of the specific IPs to send email to
hotmail.com, another for yahoo.com and all the others from the main
IP (as it is now).

Any ideas on how this can be done?

Thank you