I have a zen cart shopping site.

Its working pretty well, however it need "subscription list" fixed.
When customers emails are already in the shops "customers list", I cannot get people to add their email addresses to the subscription list.
It says its duplicated.
I think the zen cart thinks subscription list and customers list is the same thing..

I also need something like a combo plugin installed?
Like you add 2 products together and it automatically gives discount?
Say each item is $80 if you put both in the cart it gets down to $100 for both? Or 3 items together for $130? And so on..

Another thing is.. when people order using paypal express checkout, their email address doesn't get registered in the system, so I cannot send email notifications to them. I need their email address to be registered in the order tab, so I can send "order status" notifications.

I think these are pretty easy job as its pretty default stuff gone wrong. Hope to get someone who knows what hes doing.
Thank you!