Four common reasons organizations choose 01.com Zimbra hosting versus Exchange hosting include:

1. The Zimbra web browser experience (and off-line Zimbra desktop capability!)
2. Cost-effective, larger mailboxes (up to 11GB, and beyond)
3. Native Mac mail support and sync (and upcoming native Linux support)
4. It lowers costs and organizational reliance on Microsoft products and licenses
5. Also works with the iPhone and ActiveSync, plus additional features and security
   

You may want to read about Microsoft's own positioning of Exchange 2007 versus Zimbra, starting on our blog. You may also want to download a PDF of the September, 2007, Webinar by Zimbra about the differences between the products.

The following feature comparison is based on research as of January, 2008, looking at the Exchange hosting programs of both 1and1.com and rackspace.com. We welcome your comments and suggestions to improve this table. Would you like references of enterprises, including educational institutions that have chosen Zimbra over Exchange? Please contact us.

Features	01.com Zimbra Hosting	Exchange Hosting
Recurring Fees	$4.17-$6.99/user/mo	$6.99-$14.99/user/mo
Maximum Number of Mailboxes	Unlimited.	Unlimited.
Bring Your Own Domain Names (yourcompany.com)
Domain Admin / User Provisioning & Management
Maximum quota (GB/mailbox)	Unlimited (extra $1 to $2/GB/mo)	1 (5 Rackspace - $10/GB/mo or more)
Secure chat (xmpp, stored)
Task list sharing
File sharing
Document sharing and versioning
Email folder sharing
iPhone webmail, calendar and contact support
Contact sharing
Calendar sharing
Maximum attachment message size (MB)	50	10
Data Portability (move you data to another solution)	Open-standards based.	Limited. Proprietary.
LDAP Information Lookup (Mail.app, Outlook, etc.)	Included by request.
24/7 live support for Mac and Windows users	Included for every mailbox.	Windows only.
Branding - Custom Logo	Yes. Business Hosting.
Wiki / Document Sharing	Yes. Business Hosting.
Global Address List (GAL) - Company Address Book	Included.	Included.
Free/busy checking for group calendaring	Included.	Included.
Resources (IE: conference rooms, projectors)
LDAP - Open/Active Directory Integration	Built-in, optional.	Active Directory.
Instant, Self-Activation/Cancellation		Activation.
Server-side Personal Anti-Spam/Anti-Virus	Included.	Virus Only.                                 (spam rackspace)
Desktop Sync Support (Outlook, Mail.app, iCal, etc.)	Included.	Outlook only.
Blackberry OTA sync (email, calendar, contacts)	Optional.	Optional. (rackspace)
Built-in Archiving & Discovery (SOX) Solution	Optional.
Windows Mobile & Palm sync (email, calendar, contacts)	Optional.	Optional.
Web 2.0 Mash-up framework (Zimlets)	Included.
Web Identities	Included.
Terms and minimum number of mailboxes	Monthly or Annual. 1!	Annual. 5. (1and1 - 1)
Service Level Agreement (SLA)	100%	99.99% (rackspace)
External POP - Email account centralization	(IMAP, too, Version 5)
Distribution Lists (mailing lists)	Unlimited.	Unlimited.
Aliases	Unlimited.	10
Email auto-responders	User configurable.
Software as a Service (SaaS)
May be redeployed in-house, on your own servers.
Private event option in calendars
Keyboard/navigation web short-cuts
WebDav compliant file sharing (desktop & web!)
Able to restore deleted message (rollback)	30 days.	30 days (rackspace)
Fast online search - including attachments!
CalDav compliant calendaring