Question about postal rule

This is actually a rule that applies in many western countries, and HK adopted it during the colonial days. The rule basically allows someone to meet a deadline of submission by mailing the contract on the day of the deadline. Eventhough the contract will be received after the day of the deadline, it is still considered valid because it was mailed on or before the deadline date. The postmark on the mail will be the official date.

1. If you want to prove that the letter is sent, I'd suggest you send the letter using registered mail.

This will allow you to retain a record of mailing and also can be an official proof of mailing, even in the courts.

2. Moreover, it will also show exactly the time and date of mailing.

Even if the contract is lost during mailing, having the proof of mailing is sufficient to prove that you sent it on or before the deadline.