vbmail() broken

[filburt1]

My test forum won't send e-mails. vbmail() won't work. mail() does.
switch ($method)
{
case "vbmail":
vbmail($email, $vbphrase['test_vbms_email'], construct_phrase($vbphrase['test_vbms_email_body'], $method), true);

print_table_header($vbphrase['send_test_email'], 1);

print_description_row(construct_phrase($vbphrase['test_email_was_sent'], $email, $method), 1);
print_table_break();

break;
case "mail":
ob_start();
mail($email, $vbphrase['test_vbms_email'], construct_phrase($vbphrase['test_vbms_email_body'], $method));
$contents = ob_get_contents();
ob_end_clean();

print_table_header($vbphrase['send_test_email'], 1);
if (empty($contents))
{
print_description_row(construct_phrase($vbphrase['test_email_was_sent'], $email, $method), 1);
}
else
{
print_description_row(construct_phrase($vbphrase['test_email_failed'], $email, $method), 1);
print_description_row($contents, 1);
}

print_table_break();

break;
}
Thoughts? I have not set vBulletin to use SMTP so it should fall back to the mail() function which works properly (well, at least it sends something).