Mapping field 'to' box in a new email

Hi,

I have a custom entity called Admissons which contains a field called 'applicant' which is a lookup to a contact. 

When I send an email from the Admission entity using the email function on the activities pane I would like the email address linked to the Applicant to already be in the 'To' box.

Any ideas anyone?

This functionality already seems to be there when sending an email from the activities pane on Contact

Thank you in advance.

Thanks

Ben