VPOP3 is an email server for Windows designed primarily for small & medium sized businesses. It is very flexible, so should be able to do most of what you want to do with regards to emails (if it is possible, given the relevant Internet standards). Businesses use VPOP3 when they want centralised control and management of their email, and don't want to be tied to a specific provider. VPOP3 provides many facilities which are not usually available with the free email accounts provided by Internet providers, such as distribution lists, message archiving, flexible autoresponders and so on.
There are three editions of VPOP3:
oVPOP3 Enterprise - this is the fully featured version of VPOP3, and includes IMAP4, POP3, SMTP, LDAP and WebMail support, shared calendars (using CalDAV) and many more features
oVPOP3 Basic - this is a slightly cut-down version of VPOP3 that does not include IMAP4 or encrypted services and some other advanced features
oVPOP3 Home User - this is a very cut-down version of VPOP3 Basic that is limited to 5 users and has many of the business-related features removed. This is designed for people who want the very cheapest option and don't mind missing out on some features.
With VPOP3 Enterprise and VPOP3 Basic you can purchase a suitably sized licence for your requirements based on the number of different user accounts you want to have, from 5 users up to unlimited users in several steps. The cost-per-user decreases as the number of users increases.
There are several options you can add on to VPOP3, such as spam filtering, virus scanning, email-to-SMS gateway and fax server.