PHPMAILER中的TLS和STARTTLS

I'm trying to send an e-mail from my software but it started showing an error.. It was working just fine, and then this error showed up..

I've tried using SSL and TLS.. I've searched a lot about this but couldn't find anything.

require_once("phpmailer/class.phpmailer.php");
require_once("phpmailer/class.smtp.php");

$mail = new PHPMailer();
$mail->IsSMTP();

$mail->Host = "smtp.gmail.com";
$mail->Port = 587;
$mail->SMTPAutoTLS = true;
$mail->SMTPAuth = true;

The error message i received is:

The following From address failed: contato@allcomtelecom.com : MAIL not accepted from server,530,5.7.0 Must issue a STARTTLS command first. k24sm1975609oic.29 - gsmtp SMTP server error: 5.7.0 Must issue a STARTTLS command first. k24sm1975609oic.29 - gsmtp

SMTP server error: 5.7.0 Must issue a STARTTLS command first. k24sm1975609oic.29 - gsmtp

If I use SSL

require_once("phpmailer/class.phpmailer.php");
require_once("phpmailer/class.smtp.php");

$mail = new PHPMailer();
$mail->IsSMTP();

$mail->SMTPAuth = true;
$mail->SMTPSecure = 'ssl';
$mail->Host = 'smtp.gmail.com';
$mail->Port = 465;

I received this error:

The following From address failed: contato@allcomtelecom.com : MAIL not accepted from server,530,5.5.1 Authentication Required. Learn more at 530 5.5.1 https://support.google.com/mail/?p=WantAuthError 198sm2326104oie.13 - gsmtp SMTP server error: 5.5.1 Authentication Required. Learn more at 530 5.5.1 https://support.google.com/mail/?p=WantAuthError 198sm2326104oie.13 - gsmtp

SMTP server error: 5.5.1 Authentication Required. Learn more at 530 5.5.1 https://support.google.com/mail/?p=WantAuthError 198sm2326104oie.13 - gsmtp