This article is intended to assist users in avoiding data corruption in Entourage when connected to an Exchange mailbox.

Important: Before performing any of the maintenance actions described below, ensure that Spotlight is turned off. To turn it off go to Entourage > Preferences > Spotlight.
You may also refer to the Entourage article on Entourage 2008 & Spotlight.

1) Exclude the "Microsoft User Data" folder from antivirus scanning. If an antivirus program is installed, configure it to ignore the folder containing Entourage messages. By default, the folder is located in HD > Users > [User_Name] > Documents > Microsoft User Data. Intermedia performs a virus check on each email, so there is no need to perform client-side scanning on Entourage email.

2) Organize your Inbox. Work to make sure you have the least possible number of items in your Inbox. Both number and size of items are important here. Entourage downloads full messages along with attachments, so emails with attachments make a difference in Inbox size. Consider creating a folder parallel to the Inbox (not a subfolder, but on the same level as the Inbox in the folder list) and moving emails with attachments to this folder.

3) Don't create subfolders under Inbox. Please refrain from creating any subfolders in the Inbox. Some users keep their most important emails in subfolders, or archive important emails there for easy access. If you have many emails in subfolders and regularly access them in Entourage, the effect will be almost the same as having lots of messages in the Inbox. Entourage can get really bogged down by synchronizing emails in the Inbox and its subfolders. If you have any Inbox subfolders, move them to the root of your mailbox, at the same level as your Inbox is. Custom folders at the root level of the mailbox get lower priority in Entourage's built-in Sync Algorithm (keep in mind you can't modify the sync algorithm), so Entourage will sync them only when an item changes in those folders.
You may also refer to the Technet article How Does Entourage Work?

4) Organize your mailbox. Remember to delete the items you don't need any more. Archive old items which you don't access anymore but may still need. The best solution is to archive them by moving them to a local folder set (Folders on My Computer), which will free up space in your Exchange mailbox as well. If you want to have access to them at all times, like using Outlook Web Access while traveling, then move them to a custom folder created at the root level of the mailbox (parallel to the Inbox folder).
Read the Knowledge Base article on Archiving Or Backing Up Entourage Information for more information.
You may also refer to the Entourage article Backup Your Data.

5) The Entourage space limit is about 1 million emails. Entourage prompts that it is running out of space once the Entourage database is nearing 1.9 million objects. This is a limit for the number of items in the Entourage database, not the mailbox itself. An email or news message is actually two database items, and for anyone with near a million Entourage objects (messages, contacts, events, etc.), they will almost all be emails. So the limit is effectively just under 1 million messages. Entourage will notify you if you ever approach the limit.
You may also refer to the following Entourage articles:
Size Limits Of Database
You Receive An "Entourage Is Almost Out Of Space" Warning 

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