According to previous comment which pointed me to an article about Virtual Hosting in Pure-FTPd, I think that there are some misunderstanding about these ambiguous terminologies: Virtual IP, Virtual Host, Virtual Domain, and Virtual User. Before continue reading below paragraph, I just want to note that this post is based on my understanding. If you think it is incorrect, please let me know.

• Virtual IP - One machine has many IP address and many domain names. One IP address has an unique domain name. Actually, this is not the feature of application but it is a TCP/IP specfication. An service may bind only on one network interface, one IP address.
• Virtual Host - One machine has many IP addresses or many domain names. Each IP address and each domain name has independent configurations and settings. This scheme is often used in web server.
• Virtual Domain - One machine has many domain names. This machine may have only one IP address. User in one domain are not able to authenticate successfully in other domains. This scheme is often used in main server.
• Virtual User - A service has external user sources. This machine may have only one IP address and one domain name, or otherwise multiple IP addresses and multiple domain names. These external user may not be able to access other services. This scheme is often used in ftp server.

So, Pure-FTPd does support virtual user. ProFTPd does support virtual host. vsftpd does support virtual IP by running multiple copies with different settings on different IP addresses. Apache does support virtual host. Some might say Pure-FTPD does support virtual IP. I agree but virtual IP is not the same to virtual host anyway. Most hosting service has only one IP address but hosed multiple domain names. Virtual IP doesn’t work in this case.

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