I used Thai registered mail and it took 3 months for them to acknowledge it. I went to the website and found their fax number and faxed the form to them after 30 days of not receiving a delivery acknowledgment. Another safeguard was to call an agent at the websites number and explain the delivery problem and then inform then that I faxed the form.. The agent made a note and said since I talked to her by phone it would suffic. Therefore the form wasn't a problem in the timeframe posted on the for.