Current Version Is 4.2.2

Ability Mail Server is an advanced, secure and high performing mail server. With support for all standard mail protocols, including SMTP, POP3, IMAP4, LDAP and WebMail, the software can meet the needs of almost any business or home user. Ability Mail Server is fully scalable with support for unlimited users and domains, ODBC and clustering. The mail server also includes strong SPAM protection, on-server antivirus scanning, Content Filtering, IPv6 and much more.

Features and Edition Comparison
Services Free Lite Pro Ent
SMTP
POP3
IMAP4
WebMail
Automatic Sign-ups
Remote Admin
Outgoing Mail
Static Routing
POP3 Retrievals
Security Free Lite Pro Ent
Secure Login Methods
Anti-Hammering
Mail Loops / Infinite Bounce Protection
IP Restrictions
Advanced Port Control
Admin Free Lite Pro Ent
Simple User Interface
Setup Wizards
Domain Administrators
Message Control
INI Based File System
Clustering
Diagnostics
Catch-All Accounts
True Multiple Domain Support
Front End SMTP
User Features Free Lite Pro Ent
Mailing Lists
Redirection
Auto-Responses
Alias Addresses
Folder Hierarchies
IPv6 Support
Filtering Free Lite Pro Ent
Content Filtering
Antivirus Protection
Tarpitting
Grey List
SPAM Trap
Real-time Black Lists (RBLs)
Bayesian SPAM Filter
Sender Policy Framework (SPF)
Advanced Features Free Lite Pro Ent
256-bit SSL
ODBC
LDAP
Shared Address Books
Users and Accounts Free Lite Pro Ent
Maximum User Accounts 5 25 100 No Limit
Maximum Domains 1 10 50 No Limit
Free $80 $130 $200