Hi Jacob,
You would check that ‘To be emailed’ option if you wanted to send that specific estimate or batches of estimates via QuickBooks.
If you wanted to e-mail estimates via Method then you would want to customize that screen to do that. The ‘To be emailed’ option wouldn't be relevant in this case, since the purpose of this feature is to flag estimates you would like to later e-mail through QuickBooks. If you want to take a shot at customizing Method so you can e-mail estimates, as a hint; there is a 'send email' action that you can use ;)