I have this problem only with one email provider, that too for sending mails only. I can receive mails. But, when I send mails using the smtp setting the email server provider has given, the system says that it has sent the mail. But, the mails don't reach the intended recipient. The email service provider tells me that the setting I am using is correct. But, when I use a different smtp server to send (emails from this email), I am able to send them without any problem. Is there anyway I can check and find out whether the problem is with my setting in Thunderbird or with the email service provider.