Hi,
I struggled a bit with the same problem, or at least similar. WP wouldn’t send any emails, and I checked that sendmail was working etc. I’m using WP 2.3.1 on a Linux distro.
In my case, I finally narrowed the problem to wp-includes/class-phpmailer.php. On lines ~434-435 you should find this:
$params = sprintf(“-oi -f %s”, $this->Sender);
$rt = @mail($to, $this->EncodeHeader($this->Subject), $body, $header, $params);
It seems that there’s a problem with $params. I removed $params from the mail() function and now my mails get sent again:
$params = sprintf(“-oi -f %s”, $this->Sender);
$rt = @mail($to, $this->EncodeHeader($this->Subject), $body, $header);
Don’t know why, I think I’ll leave that to someone else. My guess would be that there’s something gone awry in WP’s sendmail config.
Hope this works for you as well.
EDIT: Oh, and do remember that all good children make backups if they decide to mess around with the code ??