If you want to send all results to a single destination per alert, then you can do that by using the $result.<to_email>$ notation in the "To" field using modern version of Splunk (6.2, and later according to @tfruru), as mentioned in the docs. However, this is somewhat limited. It appears that Splunk just grabs $result.<field>$ based on the first output row.
If you need to get fancy and send emails to different to address on a per-row basis, then you should checkout the Sendresults add-on by Discovered Intelligence. Emails with the same email_to field will be grouped into a single email. Very nice!
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