I am not going to talk about the advantages or disadvantages of going from an on-premises e-mail solution to the cloud (there are hundreds of pages/documents about that). I am merely mentioning some aspects of this solution that I think might be of an issue for some companies.
NOTE: Please do not take this information and 100% accurate as I still need to confirm some of them. I will be testing Exchange Online in the next couple of months, so I might post an update.
Lync Online
1. Lync technology does not support coexistence between Lync Online and Lync Server using a single domain. Therefore, it is not possible to deploy a subset of users in Lync Online and other users on-premises using a single domain name. Lync federation can be used to enable users to communicate between Lync Online and Lync on-premises deployments, however only using different domain names.
2. Federated Lync does not support file transfer;
3. Dial-in audio conferencing (the ability to dial into a scheduled Lync meeting/conference from fixed-line or mobile phones) is not provided in Lync Online, but can be achieved using third-party audio conferencing services;
4. No Lync-to-Lync high definition video;
5. There is no possibility of recording and playback of meetings;
6. No anti-malware scanning for meeting content and file transfers;
7. No privacy mode (which allows users to restrict their presence information so that it is visible only to the contacts listed in their Lync Contacts list);
8. There is no IM/Presence federation with XMPP networks (Jabber, Google Talk);
9. There is no interoperability with on-premises video conferencing systems;
10. Communicator for Mac client and Lync 2010 Phone Edition (for Lync-based IP phones) are not supported. Lync 2010 Mobile client coming soon;
11. No IM Archiving;
12. SharePoint (both Online or on-premise) skill search via Lync is not supported with Lync Online;
Exchange Online
1. Public folders are not available in Exchange Online. The solution would be to migrate data to SharePoint (either on-premise or Online) or to a shared mailbox;
a. As Outlook 2003 and earlier versions use public folders to share free/busy information, distribute the offline address book (OAB) and set Outlook security settings, these will not be available;
b. However, Exchange Online does not support Outlook versions before Outlook 2007.
2. When using Active Directory Federation Services 2.0 for single sign-on, users manage their credentials directly in their on-premises Active Directory. Users cannot change their passwords from Outlook Web App. This means that if a user’s password expires when he/she is on leave, the user will not be able to use any services (assuming the user does not have remote access to the internal network so he/she can change the password);
3. The Office 365 Directory Synchronisation tool ignores dynamic distribution groups in on-premises Active Directory, and does not synchronise these to Exchange Online;
4. Hierarchical address lists, Global Address List segmentation, custom Global Address List views, and multiple address lists per organisation are not available in Exchange Online;
5. Administrator-driven import of .pst files, using the new-mailboximportrequest PowerShell commandlet introduced in Exchange Server 2010 SP1, is not available in Exchange Online. However, PST Capture Tool (to be released later this year) will allow to do this;
6. OWA does not support S/MIME;
7. It is not possible to use BlackBerry devices to connect to Exchange Online via Blackberry Enterprise Server (coming later this year). However, it is possible to connect via Blackberry Internet Service. Research in Motion has announced a new hosted BES service for Office 365 customers that they plan to make available later this year;
8. Administrators cannot search Transport Logs, only Delivery Reports;
9. SMTP Relay: Exchange Online can be used as an SMTP delivery service to relay email messages. However, applications or services must authenticate with the username and password of a valid, licensed Exchange Online mailbox, and connect using TLS which a lot of applications still do not support;
10. Custom applications that use the Outlook MAPI library typically can connect to Exchange Online, but those that use the Exchange Server MAPI Client and Collaboration Data Objects (MAPI/CDO) for server-to-server communication with Exchange will not connect;
11. When an Exchange Online mailbox is deleted, its contents are recoverable for 30 days, after which the mailbox is not recoverable. If the user's account was deleted from the Microsoft Online Services Portal, then a call to Office 365 support is required in order to restore the Microsoft Online account so it can be linked to the recovered mailbox. It is not clear if/how a mailbox can be recovered after the 30 days period or for how long;
12. If a user wants to recover an e-mail that was deleted 4 months ago, the only option is the Dumpster. No mention of possibility of recovering single items through backup or a mailbox database restore from a specific point in time (which DAGs do not replace);
13. It is possible to configure mailbox capacity alerts for the user’s primary mailbox. However, the personal archive has a separate, non-configurable quota (quota depending on the plan chosen);
14. There is no Public/Private computer logon option in OWA and the default session time-out is 6 hours (configurable up to 24h – not sure is possible to configure for less than 6h);
15. Message size limits (by default 25MB in Exchange Online but 10MB in OWA) cannot be adjusted up or down. This value can only be “changed” by the use of transport rules to limit the maximum size of any individual attachment;
16. Exchange Online has restrictions that prevent users and applications from sending large volumes of email. Each Exchange Online mailbox can send messages to a maximum of 1,500 recipients per day. An email message can be addressed to a maximum of 500 recipients. These limits apply to emails sent within the internal domain as well as to messages delivered to external contacts. However, a distribution group that is stored in the Global Address List counts as one recipient but in a personal distribution group each recipient is counted separately;
17. Users can send only 30 messages per minute. If a user submits messages at a faster rate, Exchange Online will deliver the messages but will queue the messages at the server and throttle the rate of delivery. Not clear if this applies to e-mails sent to distribution lists;
18. Distribution Lists
a. Distribution groups that contain 5,000 or more members must have delivery management (a list of senders who are allowed to send messages to the distribution group) or message approval (one or more moderators who must approve all messages sent to the distribution group) options configured;
b. If a message is sent to 5,000 or more recipients, the message size can't exceed 2MB. If the message size exceeds the limit, the message isn't delivered and the sender receives a non-delivery report. The total recipient count is determined after distribution group expansion.
19. Moderation Lists
a. The maximum size of the arbitration mailbox is 10GB. If the arbitration mailbox exceeds this limit, messages that require moderation are returned to the sender in a non-delivery report;
b. The maximum number moderators that can be assigned to a single moderated distribution group or that can be added to a message using a single transport rule is 10;
c. By default, a message waiting for moderation expires after two days. However, the processing of expired moderated messages runs every seven days. This means that a moderated message can expire at any time between two and nine days.
Exchange Online Migration
1. Send/Receive As and full mailbox permissions are not replicated (might be available in the future);
2. Public folders are not replicated/supported.
3. Outlook Anywhere must be configured properly for RPC over HTTP access, with an SSL certificate issued by a public trusted certification authority.
