IIS Default Website for Domains that have not been setup

Some of IIS 6.0's settings can be set "globally", like the default start path of the log files. See this article on TechNet:

Changing Default Web Site Settings (IIS 6.0)

However, some of the settings you change will not affect your existing webs. For example, if you set the default path for your log files, this won't change the folder for your existing log files.

During IIS installation, default values are set for the various properties assigned to Web sites. Properties can be set at the global level, affecting all Web sites on a server, on the individual site level, at the directory level, or at the file level. IIS uses an inheritance model, which means that settings on higher levels are automatically inherited by lower levels. Settings at lower levels can be edited individually to override inherited settings from the next level up.

If you change a setting at a lower level, then later change a setting at a higher level that conflicts with the lower level setting, you will be prompted to choose whether you want to change the lower-level setting to match the new higher-level setting.

Regarding the home path of new web site: if you create a new web site, the IIS wizard will always prompt you for the path.

If you have to migrate your files to a new folder, I would do it one-by-one (if you don't have hundreds of them - then some scripting would be necessary). Be sure you test the sites and check if there are directories which needs "special" permissions.

1. For email, I don't think you can do this with DNS. The only time DNS is involved with mail is for determining which server to send mail to for the requested domain. So whilst you can have the MX records for both domain1.com and domain1.net pointing to mail.domain1.com, say, you will need to configure that server to accept mail for both domains, and route it to the correct mailbox as appropriate. Exchange will do all of the above out of the box.

For web requests, (and this answers #3 too), it depends on whether you care about the host name that ends up in the address bar of the browser. If you don't then you could just CNAME www.domain1.com to www.domain1.net, and as long as you have both hostnames as vaild host headers for the site in IIS/Apache, the page will load and all will work. I wouldn't recommend this however as all it takes is one absolute href and the user is bounced to the other domain, not to mention issues with SSL and wider business branding problems, SEO, the list goes on.

To do that properly, use a redirect rule and bounce all traffic to one domain.

2. IIS redirect is the neatest way, keeps everything consistent. You could just add A records for both in DNS and add both as accepted host headers for the site in IIS though. Up to you.

3. As 1. but bear in mind that if you want to use SSL you will need a dedicated server IP for each site, so it might be simpler to redirect everything to one place and then secure that.

HTH