Yes. Here’s how you do it:

1. Click Options in the upper-right corner of your Mail page.
2. Click Spam from the list on the left.
3. In the “SpamGuard” section, after the line “Empty Spam folder,” you can specify how often you’d like us to empty your Spam folder by selecting from the pull-down menu. We do it automatically once a month, but you can select two weeks, one week…or immediately!
4. Above your spam options, click Save Changes.