550 Mail Server Errors

im sitting on a VPS with cpanel+exim 4.66 installed. email accounts are working & i can receive/send emails. however im getting a few errors from some servers that i send email to

Code:
asdf@asdf.com.au
SMTP error from remote mail server after RCPT TO:<asdf@asdf.com.au>:
host asdf.mail.asdf.net.au [111.111.111.111]:
550 Reverse DNS is not setup correctly for this host.
At the moment, my VPS has 3 IP addresses, which are (imaginary) 192.168.0.1, 192.168.0.2, 192.168.0.3,

Exim is currently sending emails(webmail, smtp auth'd php scripts) via 192.168.0.3

my domain.com at the top level resolves to 192.168.0.1, mail.domain.com resolves to 192.168.0.3(aname - should this be a cname?) and the MX pointer record points at mail.domain.com

if i do a reverse lookup of my 192.168.0.3, it resolves to:

Code:
192.168.0.3 resolves to
"3.0.168.192-static.reverse.softlayer.com"Top Level Domain: "softlayer.com"
which is my VPS host.

Have i configured something wrong here? should 192.168.0.3 be resolving to my domain.com instead?