CB 1.8 and emails

Hi everyone, I have CB 1.8 and joomla 1.5.26 installed;also my mailer is PHP Mail function.
Activation mails are not sent after registration; i have tried to send an email to a user using the mail link provided by CB but the mail don't make it through.
Any idea?
Thanks

Actually the mail to the user did make through. So the issue that i have is that the Activation mail is not sent.

Hello.

Maybe, your web provider don´t allow e-mails, which are not something@yourwebpage.com. Then, you can´t use your personal e-mail, only e-mail, which provides your web provider. e.g. you web page is www.abcd.com and your e-mail must be something@abcd.com.