Firstly found that there was lsattr set for the file.

Tried by removing and resetting the lsattr
but no use.

Fix

Found that in whm exim config settings this should be like this

Send mail from account’s dedicated IP address Off

Reference /etc/mailhelo for outgoing SMTP HELO Off

Reference /etc/mailips for outgoing SMTP connections On

save and rebuild exim

• cPanel
• Exim