3
A better way, which would also make this the default method for users created directly in the admin area could be to change the kernel/user.php
function XoopsUser($id=-1) {
$this->initVar('...', x, x, x);
$this->initVar('...', x, x, x);
$this->initVar('notify_method', XOBJ_DTYPE_INT, 2, false);
}
where the third parameter (2) is the value it should have. Actually the best solution would be to use the constant for it - defined in common.php, I believe, and called something like XOOPS_NOTIFYMETHOD_EMAIL