122.167.242.192 is on several blacklists - probably because it's a dynamic pool address from ABTS.  Your message didn't say which one.

What relay server are you using to send mail?  If it's an ISP, maybe they need you to authenticate.

Does it happen to all mail, or just to a particular address?

Hi,

I'm new to Pmail and just installed the same. I'm able to receive mails correctly but while sending mails I get the following error.

Delivery has failed on the enclosed message for the following
reasons reported either by the mail delivery system on the mail
relay host or by the local TCP/IP transport module:

 550-JunkMail rejected - ([192.168.1.23]) [122.167.242.192] is in an RBL, see

Could someone please help to resolve it.

 Thanks & regards,

Neville