Regarding the Archive Service error: there should be a debug message in the Archive Service log file (which I think you've already found - if not, have a look at this link
) along the lines of "Error thrown in folder <foldername> message <messagesubject>". That'll give you an indication of which message caused the error.
It's quite possible that a subsequent run of the archive job will archive this message successfully; if the same message fails multiple times, the first thing to do is check whether you can open it in Outlook. We've found that sometimes messages are corrupted in the Exchange Information Store such that even opening them in Outlook causes an error. If Outlook is
able to open the message, please do let us know - it's something we can investigate further.
The Storage Service error: you're pretty close with your guesses of those filenames! Within the store, the folder name corresponds to the Exchange mailbox GUID; the filename of the .esa2 file is our message unique identifier and the ID of the file that contains the message body (.esa2 files are the result of single instancing, and don't contain the body, but a pointer to a .esa file where the body is stored).
If that file doesn't exist, I'm surprised. Windows Indexing Service is the thing that determines the list of files on disk that we need to index, so if the file isn't present, I'm not sure how Indexing Service told us to index it. It might be worth checking whether any virus scanner on the machine has quarantined the file?