Note that we are not only an alternative, but also you may use 01.com Zimbra hosting with Google Apps.

In addition to our delivering support to all of your team members with mailboxes, not only a few of your technical people, some common reasons organizations choose Zimbra over Google Apps include:

1. Free/busy time scheduling instead of calendar overlays
2. Microsoft Outlook 2003/2007 sync (mail, calendars, contacts, tasks, photos, identities)
3. Native Mac mail, ical and addressbook sync (mail, calendars, contacts, photos!)
4. Thunderbird Mac/Win/Linux mail, contacts, calendar sync
5. Mobile device off-line, over-the-air (OTA) sync, including iZimbra for iPhones
6. Firefox extension to drag and drop files into briefcases for file sharing

The following feature comparison is based on research as of January, 2008. We welcome your comments and suggestions to improve this table. Please note that we have listed current features, so this table will change as new features are released. Also note that this is not a strategic comparison. Would you like references of enterprises, including educational institutions that have chosen Zimbra over Google Apps? Please contact us. 

Want some specific examples of these differences?  See our blog:

• Zimbra vs. Google Apps: Calendars 
• Zimbra vs. Google Apps: Utilizing MetaData 
• Zimbra vs. Google Apps: Email Organization
  

Features	01.com Business Zimbra Hosting	Google Apps
Recurring Fees	$49.99/user/year or $4.99/user/mo	$50/user/year for Premier
Maximum Number of Mailboxes	Unlimited.	Unlimited.
Bring Your Own Domain Names (yourcompany.com)
Domain Admin / User Provisioning & Management
Maximum quota (GB/mailbox)	Unlimited (extra fees)	25 for Premier
Maximum attachment message size (MB)	50	20
Data Portability (move you data to another solution)	Open-standards based.	Limited. Proprietary.
Secure LDAP Information Lookup (Mail.app, Outlook, etc.)
24/7 live support for Mac and Windows users	Included for every mailbox.	Premier: only admins.
Mail folder sharing		Limited.
Secure chat	(beta)	Included.
Off-line access in web-browser
CalDav & WebDav compliant
File sharing (including drag and drop to web!)
Task list sharing
Branding - Custom Logo		Limited.
Wiki / Document Sharing
Calendar sharing & delegation
Contact sharing & delegation
Global Address List (GAL/LDAP) - Company Address Book	Included. Desktop & web.	Included. (Web-only)
Free/busy checking for group calendaring	Included.	Included. (overlays only)
Resources (IE: conference rooms, projectors)		Premier Edition.
LDAP - Open/Active Directory Integration	Built-in, optional.	API's available.
Instant, Self-Activation/Cancellation		(Activation only)
Advanced, Personal Anti-Spam/Anti-Virus	Included. Or use your own.	Included.
Desktop Sync Support (Outlook, Mail, iCal, AddressBook)	Mac, Linux & Windows.
Blackberry OTA sync (email, calendar, contacts)	Optional. BES.	Web browser only.
iPhone Support	Optional w/monthly or free with annual	Limited.
Windows Mobile & Palm sync (email, calendar, contacts)	Optional w/monthly or free with annual	Web browser only.
Web 2.0 Mash-up framework (Zimlets)	Included.	Limited.
Web Identities	Included. (+Sync to Outlook)	Included. (web-only)
Terms	Monthly. Cancel anytime.  Or Annual!	Annual. 60 days notice.
Service Level Agreement (SLA)	99.975%	99.9% for Premier
External POP/IMAP - Email account centralization		POP only.
Distribution Lists (mailing lists)	Unlimited & free.	Unlimited & free.
Aliases	Unlimited & free.	Unlimited & free.
Optional "free" version with Ads and no 24/7 support.
Software as a Service (SaaS)
May be redeployed in-house, on your own servers.
Mining user data and other info (see privacy).
Keyboard/navigation short-cuts
Published Road Map
Restore deleted messages (rollback/undelete)	30 days.
Legal Compliance (Archiving & Discovery)	Optional. Built in!
Satisfaction Guarantee	100%	None.