DNS, websever
 

i have registered my domain with register.com

I have centos 5.2 software

i have 2 static ips

1. is it required 2 DNS server for hosting of own webserver
2. for dns servers is it required static ips
3. Is it good to have separate servers for webserver and mail server
4. what type of softwares required to filter spam, viruses on mail server
5. Internet service from two different service providers is required to prevent loss of mails
6. is ssh port open is good
7. keeping webserver and mailserver on one is good
8. If webserver does not require static ip, where should we mention webserver ip on dns server or else if static ip is required where should we mention it on dns server

please clear my doubts

thanks in advance