The PST problem
Some Outlook 2007 users experience major performance problems, particularly if they are using Outlook on a notebook computer. Outlook may have trouble keeping up as they type. It may take a long time to return search results. And their entire computer may freeze for several seconds whenever Outlook sends or receives an email message. I'm seeing this issue on one of my machines now, and it is a real pain in the neck.

While I haven't seen any coverage of the RSS reflux problem, the PST problem is an issue that Microsoft is working on. According to them, the problem is caused by changes they made to the data structures of Outlook's PST and OST files to accommodate new features such as RSS feeds. Because of the new design, as a PST file gets larger, Outlook has to write data to the hard disk with increasing frequency. This causes the performance issues. The larger the PST (or OST) file, the greater the performance problem.

Microsoft has published a Knowledge Base article that describes the issue and lists several methods you can try to resolve it. Method 1 calls for reducing the size of your Exchange mailbox. It involves deleting items or archiving old items, and using Mailbox Cleanup to eliminate any unnecessary junk. Doing this makes sense whether you are having performance problems or not. You can do a basic cleanup by clicking Tools, then Mailbox Cleanup to open the dialog box shown in Figure B.

FIGURE B

It makes sense to use Mailbox Cleanup once in a while even if Outlook isn't having problems. Click picture for a larger image.

Unfortunately, Method 1 didn't resolve the problem for me. On the problem machine, Outlook still locked up the system every time mail came or went, so it was on to Method 2.

Method 2 calls for using an online mode profile instead of a cached mode profile. In other words, don't use Cached Exchange Mode. This fix is itself a problem. The point of Cached Exchange Mode is that it, "provides you with a better experience when you use a Microsoft Exchange account," according to the Outlook help system.

Still, having my computer freeze for several seconds every time a message came or went was pretty painful, so I tried this method. It didn't resolve the performance issue either. Worse, disabling Cached Exchange Mode increased my headaches by adding occasional messages where everything stopped while Outlook was trying to contact the Exchange server. That's exactly the kind of issue Cached Exchange Mode prevents, so this method was a total failure. On to Method 3.

Method 3 calls for splitting large PST files into smaller PST files. I decided to try this with my Archive PST files, which were the only PST files still in use now that I had disabled Cached Exchange Mode.

This was a real pain since Outlook doesn't have any automatic way to split big PST files into small PST files. You need to do it more or less manually, by creating new PST files and dragging messages or folders into them. Microsoft says the performance problems kick in when your PST files are greater than 2GB in size. I got mine down to under 600MB.