diff --git a/app/sprinkles/core/src/Mail/Mailer.php b/app/sprinkles/core/src/Mail/Mailer.php
index 1f957b729..2e2efa4d6 100644
--- a/app/sprinkles/core/src/Mail/Mailer.php
+++ b/app/sprinkles/core/src/Mail/Mailer.php
@@ -64,6 +64,12 @@ public function __construct($logger, $config = [])
                 $this->phpMailer->Username = $config['username'];
                 $this->phpMailer->Password = $config['password'];
                 $this->phpMailer->SMTPDebug = $config['smtp_debug'];
+		// Disable opportunistic encryption if secure is unset. This is
+		// required if you have an incorrect or invalid SSL Certificate on
+		// your SMTP host, but the server offers STARTTLS.
+		if (!$config['secure']) {
+			$this->phpMailer->SMTPAutoTLS = false;
+		}
 
                 if (isset($config['smtp_options'])) {
                     $this->phpMailer->SMTPOptions = $config['smtp_options'];