Sorry, this currently isn't possible.
Thank you for your prompt reply, and your acknowledgement raises another issue:
If all form surveys administered through FormsCentral are just anonymously ‘sent to’ and ‘received from’
respondents (except for email acknowledgements) then may I request an enhancement to the service,
which simply attaches a unique code(apart from date & time) to the response set each time a new respondent
submits a survey form.
This same code could also be attached to email acknowledgements sent back to forms central. This way at least
individual response sets can be linked to an email address. This requirement is fundamental to proper administration
of large surveys. Thanks Andrew Corbett
Thanks for the feedback. We'll consider this for a future release.