Emails don't need to have a To: header #73
Description
It's a good idea to add some recipients to an email, but these don't have to be in the To: header. Instead they could be in the "Cc:" or "Bcc:" header lines.
Because of this I think that these checks in Transport/Sendmail.php are not correct:
if (!$headers->has('to')) {
throw new Exception\RuntimeException('Invalid email; contains no "To" header');
}
$to = $headers->get('to');
$list = $to->getAddressList();
if (0 == count($list)) {
throw new Exception\RuntimeException('Invalid "To" header; contains no addresses');
}
According to RFC 5322 (http://tools.ietf.org/html/rfc5322) the only absolute necessary (as in MUST) headers are From: and Date:
The only required header fields are the origination date field and the originator address field(s). All other header fields are syntactically optional.
Of course there's usually no email that does not have a recipient, but the check should look for them in To:, Cc: and Bcc:.