Features
GroupMail is a fully featured environment for managing email, users, interface and functionality. GroupMail allows you to match features to users so that power users have the tools they need to get the work done, while casual or beginners have a useful system for the things that want to do without a steep learning curve.
Storage and Email Size20MB to 4GB per user mail storage plans available.5 users to 20,000 user plans available.Unlmited Attachment size - Based on how much free space you have.
Access
POP3, IMAP, WebMail, SMTP (through 2 ISPs, double reliability)GroupMail is connected to two separate networks, it increases the chances of you receiving your email.Email processing rules (Eg. Email Bigger than 30MB store in BIG Folder)Multilingual - Supports 10 languages (web interface) and 27 character encodings.
Spam and Secure Backup
Stealth Anti-spam features: The server does the work, without ever stopping your important emails.Your email is backed up 6 times per day and once per day off site.You can admister it with a Control Panel.
Groupware Tools & Sharing
Calendaring, Tasking, Notepad (file storage) etc...Forwarding addresses, (sales), Group Lists (like all staff), Mailing listShare mailboxes, multiple people can be using Outlook from a single mail box and monitor everything being sent and received.
Tailored Features
For some users all the features will be required, for others only a minimal set. You choose which setup you need for your team.
Administration

Web based administration, you retain control of the important parts of administering your mail server.
Administrators can, create, remove users, change passwords, change configuration of users, skins, change vacation rules and just about anything a user can configure him/herself.
MS Outlook
You can integrate GroupMail with Outlook if you prefer. We however recommend modern secure clients like Thunderbird.
WebMail
Multiple web skins, with various of degrees of features and complexity.Outlook styled interface option for ease of transitionKey feature set layout or full featured interfaceWebmail is accessible through two separate ISPs, so you can always login.Full search engine (like Gmail)27 character encoding sets: Chinese Traditional, Japanese, English, Spanish, German, French Russian, Turkish and more...
Create HTML email
VoIP/SIP/Instant Messaging (Coming Soon)
A private SIP registrar within your own domain. You will be able to talk to users over VoIP clients or Phone sets
Run your own Instant messanging network like AIM/ICQ/Yahoo
Allocate phone extensions to each person on GroupMail.
Secure email (SSL/TLS S/MIME)
SSL Encryption, for POP3, IMAP,SMTP, HTTPS, with your own digital certificateS/MIMEServer to Server encryption SMTP TLS when remote server supports it.
SMTP Relay (Outbound sending)
FloatingSMTPPOP3 before SMTP authSMTP Auth
Domain Mapping.
Multiple domains can be mapped to one single GroupMail installation. So that email sent to myname@domaina.com and myname@domain.com.hk both go to the mailbox "myname".
GroupMail is very powerful and many other features remain disabled such as LDAP etc. If you require anything.
Reliability
Unix systems tend to run for a lot longer without needing maintenance than Microsoft. Sooner or later do need maintaining and you will require at such a time.