[amy2203]

not easily built in, bcse have a pre/back order mod you can use, I think it's very popular.

Alternatively you can do something like set your stock levels artificially high, for example an extra 20, the exact number doesn't matter. Then set your low limit to that number, in this case 20, so now when you get down to zero actual stock you'll get an email reminder, even though xcart thinks you've got 20 in stock. It will continue to let people order the item.

Then modify your template so if the stock level is below the low limit level, it displays "order now for 1 week delivery" etc

hth