I am not sure when you saw that the Post Office in the Ede Norte complex was closed. I was there about 6 weeks ago. I found the workers friendly and helpful. After a bit of chit chatting, they were happy to call me when my mail came in. I also served as their mail woman, delivering a pile of mail to the guard house in Perla Marina.
I have successfully received mail (and packages) several times from the Sosua P.O. It takes 4-6 weeks and patience, but it does work- or at least has for me. I always stop in and tell them when I will be expecting a piece of mail, and then, when they call me to say it has arrived, I pick it up right at the P.O. Maybe that is the trick.
For more expedited service, I use EPS.
Lindsey