Shipping from abroad and VAT?

Hello everyone. I moved recently to Dubai. I was already living in the GCC but now with VAT, how does receiving shipments work? I used to order a lot from AliExpress and bookdepository.com and never had any issues having it delivered at a PO Box. Now I have read some stories of shipments being "detained" until VAT is paid? Can I still order from these websites (and others) into my PO Box or how is that going to work now? Will shipments get stopped? If so, where? Who do I pay the VAT to? Thanks!!

edit: the PO Box is private. It's my employer's PO Box (who is cool with us getting typical goods like books, etc. delivered there)