<a href="mailto:#appVariable.From#?subject=Re:%20#envVariable.EmailSubject#:%20Desc:%20#form.j_ave_transaction.Description#&body=Approved%0A%0A ID:%20#assignment.processId#">Approved</a>
Details:
#appVariable.From# is the sender email.
#envVariable.EmailSubject#:%20Desc:%20#form.j_ave_transaction.Description# is the entire email subject.
Approved%0A%0A ID:%20#assignment.processId# is the body content of the email reply.
Please note that you must use "%20" instead of spaces and "%0A " instead of Enter in the subject line and body. To create the text with "%20" and "%0A" you can use this page https://www.urlencoder.org/
Figure 1: Final outlook after adding lazy approval button in demo app's approval process's email tool