mail() function wont operate

hi there, I am trying to use the mail function only that for some reason it doesn't operate. I am using PHP4 on Redhat 6.2. The path to sendmail is fine, and sendmail is working fine. I double checked my inputs and they are ok, it looks like even though everything is well set it is still not working. One more important fact is that the mail functions returns "true" even though it had not sent the message. Any clue??? -- Sincerely, David Treves.