The Email Address for Federation feature supports multiple domains. The following figure shows an example of multiple email domains that are being used for federated traffic.

If the local IM and Presence Service deployment is managing multiple email domains, you must publish the required DNS SRV records for each local email domain.

For XMPP federation, the cup-xmpp-s2s security certificate must have all local IM and email domains included as Subject Alt Names.

Manually adding and editing email domains for use with the Email Address for Federation feature is optional since the IM and Presence Service automatically reads all unique domains for each of the user's email addresses and uses that information for the Email Address for Federation feature.

If you have domains that have users who are not yet configured for the IM and Presence Service but plan to configure those users, then you can manually add those domains to the IM and Presence Service using the Cisco Unified CM IM and Presence Administration user interface. A domain that does not currently have any users assigned is not automatically listed as a local email domain in the user interface.

User domains that are used for Email Address for Federation are listed as system-managed domains on the Email Domain window in the Cisco Unified CM IM and Presence Administration user interface. These are not configurable with the user interface.

Before you turn on email address for federation, you must alert the system administrator of the external domain to the following:

• You are using email address for federation, and that the users in the external domain must specify an email address when adding a federated contact to their contact list.

• If you are already federating with the external domain, and you wish to turn on email for federation, users in the external domain must remove the existing federated contacts in their contact list, and add these federated contacts again specifying an email address.

When you turn on email address for federation, you must notify all IM and Presence Service users of the following:

• Federated contacts now use email addresses rather than the user_id@domain addresses.

• When adding new contacts to their contact list, federated contacts must now use the email address for IM and Presence Service users, rather than the user_id@domain.

• Existing IM and Presence Service contacts (on the federated watcher's contact list) that were added with user_id@domain must be removed, and added again using the email address for the IM and Presence Service user.

• Any messages that the IM and Presence Service receives from federated contacts to the user_id@domain address are dropped (unless it happens to be the same as the email address configured in Active Directory, and the address configured in the users table on the IM and Presence Service).

• If IM and Presence Service users already have federated contacts on their contact list, when these users sign in to the client again, the federated contact may get a pop-up containing the email address.

Note	When you turn on email address for federation, the IM and Presence Service user does NOT need to change anything on the client when they connect to the IM and Presence Service, nor do they interact any differently with the IM and Presence Service node.

• You can add or delete only administrator-managed domains that are associated with the local cluster.

• You cannot edit system managed domains.

• You cannot edit system-managed or administrator managed domains that are associated with other clusters.

• It is possible to have a domain configured on two clusters, but in use on only the peer cluster. This appears as a system-managed domain on the local cluster, but is identified as being in use on only the peer cluster.

• For XMPP Federation over TLS, you must regenerate the TLS certificate cup-xmpp-s2s if adding or removing an IM address domain.