适用于Windows的SMTP / POP3 / IMAP邮件服务器

I'm looking for a relatively inexpensive (or free) POP3 mail server for Windows Server that will scale well. Compatible with SQL Server would be fantastic. It would also be great if it had a .net class library for performing simple functions like creating/deleting new accounts, adding aliases, etc.I'm looking for a relatively inexpensive (or fr