Getting Served Notice

[qwerty]

A few days before the middle of the month, I received a notice to vacate my apartment throught regular mail. A few days later, after the middle of the month, I received the same letter in certified mail (it was my "first notice" from the post office). Both letters gave me until the end of the month to vacate (meaning essentially two weeks notice), and were post-marked in the previous month (by a commercial office stamp rather than a post office stamp). I also found a copy of the same letter in my hallway without an envelope among the fliers that advertisers place in my mail slot. I've been advised that my notice to vacate wasn't served in a lawful manner because it did not give me 30 days actual notice to vacate. Someone else, in turn, has told me that if somebody called a "server" has a record of attempting to reach me 30 days before my vacate date, then the notice will stand, and it may simply end up "my word against his". I have no knowledge of anyone's attempt to serve me anything, and I do not know what constitutes an "attempt".
Does anyone have experience with this, or any comment on the situation?

[qwerty]

Thanks for your answer, kt.

What is "the RPAPL"?

The "conspicuous place service" must have been the letter in my hallway, although I have no idea when it was placed there. I receive tons of advertizing fliers (through my mail slot) that get swept to the side by my door when I open it, and it was buried in there. I ignore anything but envelopes on my floor, and my hallway is unlit so I barely see anything anyway. Unfortunately, I let the papers pile up. It seems ridiculous that this would constitute "notice."

The date written by hand of "first notice" is the 15th. I am m-t-m, and it is a simple notice to vacate.

[Chimera]

I'm relatively certain that the letter slipped under the door does constitute conspicuous place service. That's why the notice is served by regular mail and certified mail, so you are certain to get it.