With an exclusive domain and one mailbox from ISP, you can add or remove mailboxes at any time. That means you don't need to pay any extra money to your ISP for the mailboxes you add, perfect solution for small business.

Requirements for ShareMailPro: Your company must has a Domain. Must apply 1 mailbox under this domain from your ISP, and the ISP must foward all the messages to this domain to this mailbox .

Features:
Compatible with Win9x/WinNT
Auto recv and send mail
AntiVirus
AntiSpam
MX delivery support
Support alias mailbox
Email broadcasting
Support DUN
NT Service
POP3 Proxy
Refuse email spam
Log
Email backup
Firewall/Proxy support
Remote control
Inner mail exchange
Maillist support
Priority support

SharemailPro can support more than 100 mailboxes. The Free version only supports 5 mailboxes . For more mailboxes, register the software .