My complaint:

I have used PostNL twice to send registered mail to Canada. I pay a (hefty) postage for an envelope and receive a receipt and a BAR Code. 2 days later, I check the status under the track and Trace site, (zending niet gevonden), 4 days later, I check the status of the 3SRZ bar code, (again zending niet gevonden). Fortunately after 8 days, the envelope arrives in CA. Lets hope the 2nd time round, you also deliver! Its now 7 days (your website states 5-6 days) since I handed you the envelope in one of your post office counters!
What kind of service are you providing? Why issue us with a BAR code which can not be used to trace where the registered mail is? Its not even shown that it has been posted (at a post office)! Useless service, and to think that we are paying for this service also?? Pity you issue a BAR code, and then do not provide us even the status that you have received the envelope from me! Pull up your socks and invest in the BASIS of managing MAIL instead of providing “online shopping” options on your website. Get the core of your business in order, get your priorities in order! Good luck if you survive ……

Desired solution:

Make Track and Trace work for Registered Mail (Envelopes)!