Allow injecting an SMTP instance

changelog.md

@@ -55,6 +55,7 @@ This is a major update that breaks backwards compatibility.
 * Now checks for invalid host strings when sending via SMTP.
 * Include timestamps in HTML-format debug output
 * More reliable folding of message headers
+* Inject your own SMTP implementation via `setSMTPInstance()` instead of having to subclass and override `getSMTPInstance()`.
 
 ## Version 5.2.23 (March 15th 2017)
 * Improve trapping of TLS errors during connection so that they don't cause warnings, and are reported better in debug output

src/PHPMailer.php

@@ -1587,7 +1587,8 @@ class PHPMailer
 
     /**
      * Get an instance to use for SMTP operations.
-     * Override this function to load your own SMTP implementation
+     * Override this function to load your own SMTP implementation,
+     * or set one with setSMTPInstance.
      *
      * @return SMTP
      */
@@ -1599,6 +1600,18 @@ class PHPMailer
         return $this->smtp;
     }
 
+    /**
+     * Provide an instance to use for SMTP operations.
+     *
+     * @param SMTP $smtp
+     * @return SMTP
+     */
+    public function setSMTPInstance(SMTP $smtp)
+    {
+        $this->smtp = $smtp;
+        return $this->smtp;
+    }
+
     /**
      * Send mail via SMTP.
      * Returns false if there is a bad MAIL FROM, RCPT, or DATA input.