If you deployed Microsoft Lync Server 2010 with Enterprise Voice, you can integrate your on-premises Lync Server 2010 server together with Exchange Online Unified Messaging (UM) for Voice Mail service.
When you integrate on-premises Lync Server 2010 with Exchange Online UM, you do not require a Session Border Controller (SBC). An SBC is a SIP-aware firewall that is located in the perimeter network. An SBC is not required because Lync Server 2010 A/V Access Proxy and Edge server components provide secure Voice over Internet Protocol (VoIP) connections to Exchange Online UM. Be aware that earlier versions of Lync Server 2010 (such as Microsoft Office Communications Server 2007 and Microsoft Office Communications Server 2007 R2) are not supported for integration with Online UM because of known interoperability issues.
About integrating an on-premises Lync Server 2010 deployment with Exchange Online UM
If your on-premises mailboxes are not UM enabled and you intend to use Online UM, you should move the mailboxes to Exchange Online before they are UM enabled. If your on-premises mailboxes are UM enabled and you do not intend to use Online
UM, you should UM disable the mailboxes before you move the mailboxes to Exchange Online.
The following guidelines apply to you if you have on-premises Exchange Server 2007 or Exchange Server 2010 UM-enabled mailboxes that have to be migrated to Exchange Online. Exchange Online offers different methods to migrate Exchange mailboxes
from an on-premises server to Exchange Online. The following three co-existence states are available when migrating UM-enabled mailboxes: Note Staged migration describes the scenario when a company decides to migrate all users at one time instead of being in simple or rich co-existence for a long time. The following table summarizes the key differences between the three migration methods when you migrate UM-enabled mailboxes. Consider these differences when you select the migration method that is appropriate for you.
Rich Co-Existence
Simple Co-Existence
Staged migration
Will all voice mails in the mailbox be migrated?
Yes
Yes
Yes
Will user�s voice mail greeting be migrated?
Yes
Yes
Yes
Will user�s spoken name be migrated?
Yes
Yes
Yes
Will user�s voice mail PIN be migrated?
Yes
No
No
Does the admin have to manually UM-disable the mailbox before migration?
No
Yes
Yes
Does the admin have to manually UM-enable the mailbox after migration?
No
Yes
Yes
Can I reuse my existing UM voice mail pilot number + PBX hunt group?
Yes
Yes
No