Compacting should make the files on disk smaller and potentially the access of emails thereafter a little faster.
I say ‘should’ because compaction has what I’ll call a sordid history. In Outlook Express, compaction was a land mine.
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Outlook Express couldn’t handle a couple of situations, such as really large email folders. Some people would click Yes to compact their files and half of their email would disappear. That’s not supposed to happen.
As a result it’s one of several reasons I recommend leaving Outlook Express behind.
I haven’t heard of it happening with Windows Mail, Windows Live Mail or Outlook, which all use completely different storage technologies.
So what does it mean? Why do we need to compact in the first place?
Compaction is all about file space
When you delete a file, your machine doesn’t remove the file, but simply marks the space as free.
With email, the same thing happens. When you delete a message, your email program moves it to your trash folder. Then when you empty that, the message is marked as being deleted. It’s not physically removed, you just don’t see it any more.
After you’ve emptied your trash, the message could theoretically still be there taking space (even though you would need special tools to even try to recover it).
Now, if this happens over a long period of time (say you’ve received a gigabyte of email, but you’re only keeping 100 MB of it), that means there could be as much as 900 MB of email that you’ve deleted still taking up space on your hard disk and in your email folders.
When you compact, all of your permanently deleted email gets deleted for real. The files are rewritten so they only contain the mail that you actually have. As a result, the mail has a smaller file size and it becomes slightly faster to access because the messages are closer together. That’s all that compaction really does.
Should I compact?
If you’re at all unsure or scared about compaction, backup first.
Just take an image backup of your system. Hopefully, you’re doing that already. Then fire up Windows Mail and let it compact. Once it’s done, poke around and see if anything is missing. I’m certain that nothing will be. And if nothing is, then you’re done.
If something is missing or goes disastrously wrong, then restore your machine from the backup. But I don’t believe that’s going to happen unless you’re running Outlook Express.
Compacting and Outlook Express
Now, I honestly believe that if you’re running Outlook Express, you really need to consider using a different email program. The issues that I’m covering here with respect to compacting are only the tip of the iceberg. And Outlook Express is no longer being supported by Microsoft, so the issues will never be fixed.
If Outlook Express ever asks you to compact, don’t. The compact message may appear a lot – this is another bug in Outlook Express. You could compact one day and the application would ask you to compact the next even though it doesn’t need it.
Like I said, these are issues with Outlook Express. They’re not going to get fixed, so just don’t compact if you’re running Outlook Express. It’s simply too risky. I’d rather recommend that you move to a different email program like Windows Mail, Windows Live Mail, Thunderbird, Outlook, or going online with something like Gmail. Almost anything other than Outlook Express is a much safer approach to preserving your email.