Office 365 limits - Exchange online vs Exchange on-premise

I like Office 365 and I encourage every organization to at least consider it seriously.
So none of my points is against Office 365 but I think a few things should be known. All is public information, but hard to get a comprehensive view.
I know that I am limited: in time, in money, in material, in knowledge, get allowance, etc. pp.
So your on-premise Exchange setup has limits to, mailbox size, size of an email, size of attachments, number of recipients in one email and so on. Some are set by an administrator, others are predefined or are technical limitations. And your smart users have probably already figured out how to work around. :-)

Notes:
- Cloud services features and available resources are changing frequently. So take that list as an start point, but not as a final and complete list.
- And by the nature of cloud services you give up (good or not) a lot of your administrative burden and permissions.
- And some limitations are less important if you still have a on-premise Exchange, e.g. for fax gateway integration, Blackberry BES
- Before you start a pilot or start the migration take some time to write up a service description of your on-premise messaging environment with all the different views: end-user, mobile end-user, administrators, auditors, change management
- All information is in regards to Office 365 E plans (http://www.microsoft.com/en-us/office365/buy-midsize-enterprise.aspx?WT.z_O365_ca=Buy_how-to-get_en-us#fbid=9hDlNaUhDNH)


Features:
- No public folders available and cloud users do not have access to on-premise public folders
- No delegation access between cloud users and on-premise users
- No S/MIME support in OWA, even not you install the SMIME ActiveX control manually
- S/MIME certificates are not synchronized to O365 via Dirsync, OL GAL export works but is a unmanaged and end-user driven tasks
- Access to O365 Exchange is over HTTP RPC and web services, if you have a MAPI only application that will not work with O365
- OWA 2003 cannot access free/busy information from cloud users
- ActiveSync does not support certificate based authentication
- Exchange 2003 organization must be in native mode, not in mixed mode for Hybrid server setup


Exchange related:
- More network bandwidth for Internet access
- Groups with over 15.000 members not sync
- Dynamic groups ignored
- 25 GB storage limit for each mailbox, wit E Plan 2 users can store more data in personal archive
- You cannot move mail box items larger than 25 MB to O365.

- Inbox folder: 20,000 items
- Sent Items folder: 20,000 items
- Deleted Items folder: 20,000 items
- Calendar: 5,000 items
- Contacts: 5,000 items
- Message limit 25 MB (OWA 10MB)
- Size of a single mailbox item ??

Lync related:
- Lync Online does not work with room-based conferencing systems
- must have a different SIP domain (real coexistence is not available)


SharePoint related:
- 20.000 user limit (hope to see that increased soon)
- no federation search




Find more at
http://community.office365.com/en-us/f/183/p/1541/5095.aspx
http://www.microsoft.com/download/en/details.aspx?id=13602