If you’re trying to conserve disk space, and you’re a user of the built-in Mail application, you may be overlooking one source of disk space usage: attachments on e-mails you’ve received. By default, Mail leaves all attachments alone, even if you save them to another spot on your hard drive. Over time, you can build up quite a collection of old attachments. Deleting these—assuming you’ve saved them elsewhere and no longer wish to keep them in Mail—can save a fair bit of drive space. For example, on my machine, I have roughly 400MB worth of attached files, even though I’ve saved all those files to other spots.
If you’re running the OS X 10.4 version of Mail, you can use a Smart Mailbox to help manage your attachments. Select Mailbox -> New Smart Mailbox, and when the dialog box appears, give your new mailbox a useful name such as Messages with attachments . For the rules, just set the pop-up to Contains Attachments and click OK. That’s it; your newly-created mailbox now contains a list of every e-mail you’ve received that has an attachment.
Once you have the mailbox set up, you can use it any number of ways. Leave the view sorted by date to see your oldest attachments; these might be good candidates for deletion or attachment removal (Message -> Remove Attachments). Alternatively, click the Size column header to sort your attachments by size, and then scan those messages with large attachments. If you know you’ve already saved those attachments, delete the message or remove the attachment. You can even remove attachments from multiple messages—just select them using Shift and/or Command clicks, then choose Message -> Remove Attachments, and they’ll all go poof!
Just make sure you have a backup before you try this, just in case that one critical file from the boss accidentally gets removed without your realizing you had yet to save it!