Can Heidi's agents send emails or messages on their own?
By default, no. Outbound messages to real people are a high-blast-radius action class: they default to draft-and-confirm, because you cannot unsend what someone already read.
The agent does the work, drafts the message with full context, and a human presses send. That is deliberate: the cost of one wrong autonomous message to a customer outweighs the seconds saved on a thousand right ones.
Receipts apply here too: when a message goes out, the delivery confirmation is on record.