How to delay automatic retainer invoice

How to delay automatic retainer invoice

Hi,

we would like to use the functionality that there is a retainer invoice created automaticaly, when the customer accepts the offer.
The "problem" is that the mail with the retainer invoice is sent imediatelly to the customer, which is kind of "impolite".

So the question is, how to delay the automatically sent mail with the retainer invoice by a adjustable delay?
It would be great if I could setup a delay of e.g. 8h or 1 day, etc.

Thanks and BR
Patrick