I’ve been using bongous.com . They are more for packages than mail. You get your own address (their address, just "suite number such-and-such) in Connecticut. They unpack, inventory, and weigh everything you receive. Then when you are ready you pick some or all of your stuff, and they consolidate it into one shipment. They try to fit it together so you don’t get hit with volume-weight fees. They only ship out using DHL Express (Air). But because they do a massive volume with DHL, they get a big kickback from DHL. And they pass this on to you, with like 50% off on the DHL rack rate. Plus the consolidation is a saving. Anyway they explain it and calculate sample rates if you go to their website. They have 2 different levels of service, one is $15/mo (3 month minimum) and includes consolidation, the other is like $5 per shipment but no consolidation so you might end up with a bunch of shipments and less of a kickback kickback. One advantage of a CT address is I believe no US sales tax in that state. And also international shipping seems to me the same price no matter what state it originates from.
There is also usglobalmail.com/ if you have used them please add to this thread. I think there are other such services in USA and other countries. US global mail is in Texas, so you might get some sales tax. Though if you ship from Amazon you won’t, its just that larger businesses that have an office in Texas will have to charge you TX sales tax. This place offers more outbound shipping options than just DHL. Like, they offer USPS Global Priority Mail, like $16 for up to 4# to Taiwain IIRC. So that would be a lot cheaper than DHL. And FedEx might be cheaper than DHL, though they don’t deliver to every city in Taiwan, anyway check the rate calculator.
I shipped a package or two on my own from a friend’s house before I discovered these. Its a huge nightmare of paperwork, and then at the end you will pay the full rack rate from DHL or Fedex, so buy some vaseline too. Also, as far as customs here goes, what I hear is, for packages with over $300 declared value, they just pick them at random and sometimes you get hit with duty of like 5%. Or maybe more, depends on what’s inside, in fact, you might check, there are many things that are prohibited, e.g. projectors made in china, etc.