Use Mail/newsletter function to individual email address

Hi,

I would like to know if it is possible to modify the inbuilt Mail function so that in addition to "Customer" it is also possible to enter an individual email address and send it to just that?

EG: If a customer uses Guest checkout they cannot be selected from the list of "Customers" - I would still like to be able to email them from Opencart's Mail (newsletter) editor by entering the email address manually.

Does anyone know of an easy modification to do this?

OC 1.5.6 with lots of mods incorporating some CE fixes and other fixes up to 1.5.6.4

TIA,

Stokey

how about using an extension like this?

https://www.opencart.com/index.php?rout ... n_id=21469

Thanks rjcalifornia, but I am on OC1.5.6 plus mods and that is only for 2.0+