Mails are getting bounced back
If your email is getting bounced back, you should have complete error details that are given in the bounced e-mail.
126.96.36.199 does not like recipient. Remote host said: 550 5.7.1 <ilfsecosmart.com>: Helo command rejected: You are not me Giving up on 188.8.131.52.
The error comes if the reverse dns of the outgoing IP does not match with the Helo greeting sent with every smtp session.
Edit the following file
Put the URL set for the reverse dns entry of the outgoing ip Restart the qmail queue service