It doesn't cost much, but it's not safe
It is suggested that the landlord send it by express delivery!
Weigh this letter at the post office. If the letter is 20g or less, if you choose surface mail (that is, directly drop it into the post office mailbox), the fee will be 1.20 yuan.
If you choose registered mail (you need to hand it over to the post office counter), you need 4.20 yuan postage (registered mail is safer).
If it is more than 20g, you need to add 1.20 yuan postage for every 20g.
If your mail is 2 1g and surface mail, the postage is 2.40 yuan.
If you send it by registered mail, the postage is 5.40 yuan.