The name of the amavisd script may vary depending on the linux distribution. In your case it might be named e.g. amavisd-newrun:
As for the second part of your post could you tell me if can i use my server ip address instead of domain name? It is because there is no specific fqdn pointing to my server, all are handled by ispconfig and redirected to client directories. I will be glad for some more help. Thanks.
No, you have to use a fqdn. See here on how to access a server if you have not registered the domain name yet: