I have one user who has a problem where they were sent an e-mail, but didn't get it in their Outlook Inbox, but it showed up fine in their Inbox on their iPad. Is there a particular log I can check or read that shows what e-mail message(s) went to what devices? Is this a common occurance?

Just to confirm, the iPad is using the integrated Microsoft Exchange ActiveSync client correct? If the user originally configured the iPad using the wrong client, such as the Microsoft Hotmail settings, this would not use ActiveSync but POP or IMAP, which could cause the device to pull down new messages and remove them from the Exchange mailbox. This would occur if they opened the message on their iPad before using Outlook was able to sync the mailbox.

Yikes, I will check this. I assume it's the integrated Exchange ActiveSync, since it shows up as a mobile device when I go to manage said user. Will report back. If it ends up being Exchange ActiveSync, then what? D: Edit: The use doesn't have their iPad for me to check, but I recall using the built in client. What else should I be checking or looking into? When I looked at message tracking logs, it only tells me that the message was successfully delivered: there's no easy way to tell to what device(s) & inbox it was delivered to, correct?

If the iPad is using the Microsoft Exchange ActiveSync based configuration, then the issue still exists. Is POP or IMAP enabled on the Exchange 2003 server? If not, then the iPad shouldnt be connecting using a wrong configuration, such as the Hotmail client.

It's Exchange 2010 - I typically just use whatever default app or connector is on the device. If it says Exchange, or an Enterprise Exchange environment, I use that because I know it's correct. Thankfully, the user hasn't noticed any other e-mails that have this problem or issue, but I'd still at least like to know either: why it happens, or where I can check logs to see what is ineed happening for future. I know you can look through/parse the logs in C:\inetpub\...\, but that seemed to only tell me the devices that were connected, and the messages. It didn't show the actual messages, subject lines, etc.

The Exchange message tracking will only log the message routing events. Once the message is received by the user mailbox within Exchange, message tracking determines that to be a successful delivery and does not track any other operations on that message performed by clients. You may be able to get details you are looking for by enabling mailbox audit logging (http://technet.microsoft.com/en-us/library/ff459237.aspx). This would only be helpful for future occurrences of the issue though. Unlessyou can recreate the issue, you may not want to leave logging enabled indefinitely.

Understood. I'm going to make this as an answer becuase you've posted and replied quite a bit to help me. Hopefully, these posts don't disappear anytime soon. :) Thank you.