I send a mesage = Я отправил сообщение = Я послал сообщение ( two most used variants) We must be very carefully with "send = послал" when we use it for person. It's better to say "I dirrect him = Я направил его" Because "я послал его..." is very same to "I say 'fuck you' to him" Sorry

This letter has been sent - Письмо отправлено I have sent him to the lab -Я послал его в лабораторию

Thanks... As far as i understood посылать & отправлять will be enough to handle sentences where someone sends something.

I've asked a similar question before. Perhaps some of the answers may be of help: http://www.italki.com/question/229510