I've used Caribe Tours for years. Put your name and phone number on package as sender and name, phone number, and address, if you know it, of the person to receive the package. Caribe Tours will charge you a fee and give you a receipt. When it gets to Santo Domingo, the person you sent the package to will get a call from Caribe Tours. The person goes to Caribe Tours with ID and picks up the package.
Keep in mind that if you address it to a particular person, that person will probably have to pick it up. If you are sending it to an office, for example, better to address it to the office. You can put down at the bottom, Attn: name so that the office will know who gets it. But meantime, anybody from office can pick it up.