It's mostly there for logs and internal results reporting. Cron output (and IIRC metrics reports if you turn them on) are sent to it for instance, so if you wish to see these, this mailbox is where you look. Other than that, yeah, it mostly collects spam. I have 3 spam emails and 45 messages full of cron results in mine right now. If you're really worried about it, you can probably code a script that connects the mailbox and deletes all the mail. I never had to empty mine in the 5 years I had a Stevie account, so it's unlikely to ever hog a massive amount of space. My Tommy account has 48 emails in there currently.