Because of a job offer, I am moving out of the country before end of May, hence, I want to terminate my lease a month earlier than I planned. I am trying to beat the three-month notice period. My question is, if I mail my letter to the landlord tomorrow by priority/registered mail such that it will reach him by Monday, February 29, is that enough? Or he has to acknowledge the receipt of the letter? What if he's not there to receive it on Monday? Also, should I send the letter only to the owner, or to the immobilien (company) as well?

Thanks.