Do i need Bind for the normal function of IMSCP. When I manage my dns record on another server what about local resolving of subdomains alias etc. is therefore bind necessary?
If you use your own DNS server, there is not need to install Bind9 on i-MSCP server. During i-MSCP setup (or reconfiguration), you can choose the "external server" option to avoid to install Bind9.
In such case, you must ensure that your system can resolve DNS names by adding one or many nameserver entries in your /etc/resolv.conf file. Generally, when you get a new server, that file is filled with the DNS from your provider. From my side, I use the google public DNS:
BTW: I answered here but note that we are not here to teach you. You should search a bit before asking such question.