If it exists, it would be in the logs, and may require a higher level of logging. However I do not suggest you run with a higher level of logging by default.
Perhaps you can clarify the use case where you require evidence that the email was sent. Some customers send notices to a distribution list, which then they control via their mail system. That way you could include an email accounton that distro list which could be used as an audit trail of all outbound messages.