If you want to confirm this, use ADSIEdit to view the properties for a problematic mailbox and check the value of the showInAddressBook attribute. If you compare this with a good account, you'll note that all good accounts have this attribute populated whereas problematic accounts don't. That said, you may find that accounts suddenly start working after a given time period has elapsed, in which case your RUS is taking some time to stamp the new accounts. If, however, your RUS never seems to stamp these objects no matter how long you wait, then you've got either a problem with RUS configuration or one with permissions.
See the following Microsoft Knowledge Base Articles to resolve these issues: 319065, 287137, 286356 and 297124. After that, your newly created accounts should be able to access their Outlook without having to be made administrators in your domain.
Dig Deeper on Legacy Exchange Server versions
Have a question for an expert?
Please add a title for your question
Get answers from a TechTarget expert on whatever's puzzling you.