There are a lot of remedies for Outlook PST files that are broken. I learned a few dozen over the weekend while trying to fix my own. Unfortunately, in the end, I had to create a new file and let that be my main outlook file, but I thought I would share the variety of solutions I discovered.

The chase began when I got a message from Outlook that my SENT folder had reached it's limit of how many items can be in it. I hadn't archived since May, so it was time. But when I attempted to archive it failed. It was so long ago, I can't remember the error, but it was strange.

So I tried to delete some of the files in my SENT folder and got the message "Folder is full".

There weren't a lot of messages in my delete folder, but I right clicked on it and chose Empty Deleted Items. Now I got a very interesting message. (For search engines it's "The messaging interface has returned an unknown error. If the problem persists, restart Outlook."

Restarting Outlook did not fix the problem.

Installing the new Office 2007 Service Pack 1 did not fix the problem. This one was a real time-sucker, but I needed to do that eventually anyway.

Out of curiosity, I tried the Empty Junk Mail folder option and got this interesting result.

I went from 3 items in the mail folder to 4.3 billion! That's probably how many we get in a year, though, right?

So, over the next day and a half, I tried everything from running checkdisk on the disk, defragmenting that drive (40GB of data ... imagine how long this took!) and more.

Even trying to copy the file failed with a "cyclic redundancy check" error.

With all of this, happily the file continued to function almost normally. I can use it in Outlook and get at all of my emails.

Here are some of the tricks I tried as well. Even though my problem was so bad (clearly a bad spot in my outlook file), that they didn't work for me, they are definitely very valid solutions for more more common scenarios.

Outlook has it's own tool for fixing PST files called SCANPST.exe. It's a little UI that can be found in Program Files\Microsoft Office\Outlook12 (for Outlook 2007). There's a version for 2003 as well.

Unfortunately, during the first check, it consistently stopped at 60% saying that I needed to run chkdsk on my drive and then try ScanPST again. This happened after I did the chkdsk. Here's a Microsoft KB document about this tool.

There's also a solution that works for many which is to recreate your Outlook profile. This didn't work for me either. Here's a great blog post on how to do that , just in case it is the trick that works for you. I started by copying my profile so I wouldn't have to recreate my accounts but that didn't work. So, in case my laziness was the problem, I created one from scratch (after making a list of all of my email accounts) but that didn't help either.

Another solution is to create a new Outlook file and import the items from the old file into it. This didn't work, though it did get a number of emails into the new file before it failed. And when I separately imported the contacts, that worked perfectly. Here is a Microsoft support document that walks you through this solution.

In the long run I ended up with a new outlook file that has a lot of my previous email in it (and happily a good chunk of my folder structure) and I am using the old outlook file as an archive file. Every time I get an email that is involved with a rule, I have to modify the rule to point to the same folder int he new file. But I finally just gave in on this battle and took what I could get for a solution rather than trying to fix the actual problem. I'm a pit bull, and it took me about 15 or 20 hours before I would give up. Some day I'll learn!