If you are planning to deploy Exchange Server 2007 Service Pack 1. It is highly recommended to read the article provided by Anderson Patricio from MSExchange.org website. He explained different scenario's on how to install Exchange Server 2007 SP1.

To start your upgrade, continue reading the article posted here: http://url.king.net/exchange2007sp1

To increase  your knowledge in managing Exchange Server 2007. I recommend you to read the article written by Neil Hobson about Exchange Server 2007 Permissions and Roles. Here's the link: http://url.king.net/exchangepermissions and Part2 http://url.king.net/exchangepermissions2

How to Grant Full Mailbox Access permission? You can Add-Mailbox Permission from shell to assign it. For example, we can assign Full Mailbox Access permission on John Smith (jsmith) mailbox to another user John Doe (jdoe).

From the shell command, type the following:
Add-MailboxPermission "jsmith" -AccessRights FullAccess -user "jdoe" [Enter]
and if doesn't work for you, try this alternative command:
Add-MailboxPermission jdoe -User jsmith -AccessRights FullAccess

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References:

• Deploying Exchange Servers 2007 SP1. Retrieved last September 17, 2010 from http://url.king.net/exchang2007sp1
• Exchange Server 2007 Permissions and Roles. Retrieved last September 18, 2010 from http://url.king.net/exchangepermissions and Part2 http://url.king.net/exchangepermissions2

Reading Materials:

• Exchange Server 2010 Unleashed
• Microsoft Exchange Server 2007 X64 5 Client
• Microsoft Exchange Server 2007: The Complete Reference
• Microsoft Exchange Server 2007 For Dummies