Dear Ken, John and Clay,
Thank you so much for your contributions and your detailed explanations dealing with the error. #John, I have seen the last screen shots of your system, I have tried out that too but nothing has changed. Even I have set up another SMTP (gmail), but that did not work either. #Ken, I have just attached the screen shot of the php.info site that you asked. Actually, I had also doubts about the settings of the database, particularly the settings of sendmail_path but our IT expert has informed they are correct, and it has been proved by you too. However, I still want to ask if "sendmail_from" has got the correct setting since it says it is set as "no value" ("0", not "1" in the database) which may mean, "do not send e-mail" !? Tomorrow I will get into touch with the responsible person with the mail server and if that solves the problem, I will just inform you all.
Best...
Erdal Ayan, MA