What are some common reasons for emails being flagged as spam?

Common reasons for emails being flagged as spam include using spam trigger words in the subject line or content, sending emails to large numbers of recipients at once, using misleading or deceptive subject lines, and not having proper authentication set up for the email server. 

// Example PHP code to avoid emails being flagged as spam by using proper authentication

$to = "recipient@example.com";
$subject = "Your subject here";
$message = "Your message here";
$headers = "From: yourname@example.com\r\n";
$headers .= "Reply-To: yourname@example.com\r\n";
$headers .= "MIME-Version: 1.0\r\n";
$headers .= "Content-Type: text/html; charset=ISO-8859-1\r\n";

// Set up SMTP authentication
ini_set("SMTP", "mail.example.com");
ini_set("smtp_port", "25");
ini_set("sendmail_from", "yourname@example.com");

// Send the email
mail($to, $subject, $message, $headers);

Keywords

email deliverability spam filters email authentication DKIM SPF

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