Nadya,

>BTW, I sent some private messages to other members and never received answers.

FWIW, I usually look at the icon and number of private messages now and then and try to keep up with the last one I looked at (what was the number the last time I looked)? Sometimes I keep messages there that I want to refer back to later.

However, I have sometimes gone several days without noticing that someone sent me a private message, so if it's really urgent and you are not already in a private message conversation with someone, email is probably better.