I used to work in the financial industry and dealt with lots of contracts that had to be sent back and forth. The vast majority of these documents had to be sent overnight. Of all the services we used DHL was BY FAR the least reliable.
I do the same now - the one we seem to have the best luck with overnight is FedEx - in 10 years of me using them, I have only ever lost one package - and it was actually one sent to me by @phillipma1957 and that was like 2 weeks ago that they lost it - they promptly paid the claim, they accepted the blockchain transactions and our pms here as evidence of value/expense.
DHL... oh boy 3 lost packages and several destroyed but arrived packages and the majority of them late.
UPS... maybe a dozen or so that end up late but never lost any.
USPS... actually pretty reliable but slow - though I got a registered mail from Great Britain that was supposed to be signed for and not bent - it was shoved in my mailbox so was bent and had a hole in it. Oh, and they did not get my signature. The peelable sticker which they are to take and return to sender for verification of receipt was still on the envelope. That was yesterday.
For digital assets - use a courier if its valuable, the expense will most likely be worth it.
