What is the ruling on dealing with an e-warehouse company that provides goods and undertakes packaging and shipping in exchange for a monthly subscription?

It is not permissible to sell what one does not own, nor to sell what one owns before taking possession and acquiring it. For example, if you buy a product from a warehouse and ask them to ship it directly to the customer. An exception to this is Bay' al-Salam, which is selling something described in detail, with delivery deferred to a known future date, provided the full price is paid at the time of sale. After this, it is permissible to buy the product and ship it to the customer. It is also permissible to act as an agent for the warehouse or the customer for a known fee; in this case, ownership of the product is not required, and the warehouse may ship it to the customer. There is no harm in paying a monthly fee to the warehouse for packaging and shipping if the items to be packaged and the shipping destination are known.