Postfix Email Problem

From Few days we are getting weird problem with postfix there is attempt to send many emails thru the CWP panels from non-existing email accounts on server how this is possible ?

probably hacked website, you need to check the logs are clean account from the malware

This could be a serious issue and should be done properly by the experienced sysadmin or cwp support from the start or the malware will expand and it will be in the backups and you will not be able to recover that site anymore ...or the only way will be to remove all files and install all new.

Also if you don't have cwp secure kernel that kind of malware could expand on other accounts.

but this is CWP Admin panel on that subdomain there is no Site

you need to check the logs and mail headers...however, if you event don't know those basics then you should check with experienced sysadmin or cwp support