Hi, We did a migration and conversion from v.1.16 to 1.25.3 on a new server, using XAMPP as our base. Generally, it worked well, thanks for that! We have a lingering problem, however, in sending email, including confirmation messages, password resets, etc. No mail is sent, and the error, "Unknown error in PHP's mail() function." is returned. Google suggests two small changes in the UserMailer.php file, both having to do with the $headers variable. Neither fix works, however, in our case. I've scanned the archives of this list back to January, and didn't see anything there that seemed like this problem. Can anyone point me in the right direction? Many thanks! Cal Frye