phpmailer gmail emails go to spam - php

Question

I know this question has been asked before but my issue is a bit different. I use the php mailer to send a bulk of mails in a loop to customers from the database. In the body of the mail when there's no html stuff like body = "hello" the emails get delivered to the normal inbox. However, when I use html tags in $mail->Body then the email goes to spam. The code I use:
$mail = new PHPMailer;
$mail->isSMTP(); // Set mailer to use SMTP
$mail->Host = 'someone'; // Specify main and backup SMTP servers
$mail->SMTPAuth = true; // Enable SMTP authentication
$mail->Username = 'someemail.com'; // SMTP username
$mail->Password = 'password'; // SMTP password
$mail->SMTPSecure = 'tls';
$mail->From = 'someemail.com';
$mail->FromName = 'Mailer';
#$mail->addAddress($email); // Name is optional
$mail->addAddress('someemail.com');
$mail->AddEmbeddedImage('rr.jpg', 'logoimg', 'rr.jpg');
$mail->AddEmbeddedImage('bottom.gif', 'bottomimg', 'bottom.gif');
$mail->WordWrap = 100; // Set word wrap to 50 characters
$mail->isHTML(true); // Set email format to HTML
$username = "123";
$mail->Subject = 'Welcome';
$mail->Body = "Hello, welcome"
$mail->AltBody = 'Welcome ';
$mail->send()
The issue is only with gmail. All other major mail providers such as yahoo, hotmail and live are fine. The emails go to inbox. It may be because I use quite a lot of html, colors etc in the email. But I don't know why gmail moves the mail to spam simply because it looks like many other spam mails. Is there any solution?