Starting with Outlook 2010, we introduced a new feature that allows users to add Multiple Microsoft Exchange accounts to the same profile:
http://office.microsoft.com/en-gb/outlook-help/what-s-new-in-microsoft-outlook-2010-HA010354412.aspx : "What's new in Microsoft Outlook 2010"
Outlook 2010 added the capability to connect to multiple Exchange accounts within the same profile. This has been a frequently requested feature in earlier versions of Outlook, and it is finally here in Outlook 2010.
This feature is useful, for example, when you have multiple Exchange accounts in different organizations. In earlier versions of Outlook, you had to use multiple Outlook profiles to work in either Exchange mailbox, causing you to restart Outlook every time you wanted to check e-mail in the account that is not currently in the active profile. Or, you can use a single Outlook profile but one account would be configured as a POP3 account. In this situation in Outlook 2010, you can have both Exchange accounts in the same Outlook profile, allowing you to send and receive e-mail in either account as if they were the only account in the profile.
Please keep in mind the following limitations about the number of Exchange accounts you can include in the same Outlook profile.
Additional Exchange Account supportability:
Adding an additional Exchange account depends on the following conditions:
However, if you grant Full Mailbox permissions with the intention of adding a secondary exchange account, you should be careful to avoid conflictual overlapping settings. Automapping* or other type of permissions granted on a mailbox can interfere in the behavior of an additional account.
Issues can occur when you add multiple Exchange accounts in the same Outlook 2010 profile in some configurations. Therefore, there are some supportability limitations when using this feature.
The below table is a graphical overview of the information available in the article: http://support.microsoft.com/kb/981245: "Issues that can occur when you add multiple Exchange accounts in the same Outlook 2010 profile" and it is intended to describe the supportability of Additional Exchange accounts under the same profile:
Note: Please remember that in a manager delegate scenario, adding the manager's mailbox as an additional exchange account is not supported.
http://blogs.office.com/b/microsoft-outlook/archive/2009/08/25/multiple-exchange-accounts-in-outlook-2010.aspx: "Multiple Exchange Accounts in Outlook 2010"
Please feel free to comment or add any suggestions.
*Automapping = In Exchange 2010 Service Pack 1 (SP1) Exchange introduced a feature that allows Outlook 2007 and Outlook 2010 client to automatically map to any mailbox to which a user has Full Accesspermissions. If a user is granted Full Access permissions to another user'smailbox or to a shared mailbox, Outlook automatically loads all mailboxes to whichthe user has full access.
Microsoft Exchange Server 2010 Service Pack 1 (SP1), Outlook 2010 and Outlook 2007 clients automatically map to any mailbox to which a user has Full Access permissions. If a user is granted Full Access permissions to another user's mailbox or to a shared mailbox, Autodiscover automatically loads all mailboxes to which the user has full access. If the user has full access to a large number of mailboxes, performance issues may occur when starting Outlook. For example, in some Exchange organizations, administrators have full access to all the mailboxes in the organization. In this case, upon starting, Outlook tries to open all mailboxes in the organization. Please consult the following articles for additional information: