DEBUG step 2

src/PHPMailer.php

@@ -1465,21 +1465,26 @@ public static function idnSupported()
      */
     public function punyencodeAddress($address)
     {
+echo '==================================', PHP_EOL;
+echo 'Received input: ', $address, PHP_EOL;
         //Verify we have required functions, CharSet, and at-sign.
         $pos = strrpos($address, '@');
         if (
             !empty($this->CharSet) &&
             false !== $pos &&
             static::idnSupported()
         ) {
+echo __LINE__, ' - in if condition', PHP_EOL;
             $domain = substr($address, ++$pos);
             //Verify CharSet string is a valid one, and domain properly encoded in this CharSet.
             if ($this->has8bitChars($domain) && @mb_check_encoding($domain, $this->CharSet)) {
+echo __LINE__, ' - in second if condition', PHP_EOL;
                 //Convert the domain from whatever charset it's in to UTF-8
                 $domain = mb_convert_encoding($domain, self::CHARSET_UTF8, $this->CharSet);
                 //Ignore IDE complaints about this line - method signature changed in PHP 5.4
                 $errorcode = 0;
                 if (defined('INTL_IDNA_VARIANT_UTS46')) {
+echo __LINE__, ' - in INTL_IDNA_VARIANT_UTS46 condition', PHP_EOL;
                     //Use the current punycode standard (appeared in PHP 7.2)
                     $punycode = idn_to_ascii(
                         $domain,
@@ -1488,18 +1493,22 @@ public function punyencodeAddress($address)
                         \INTL_IDNA_VARIANT_UTS46
                     );
                 } elseif (defined('INTL_IDNA_VARIANT_2003')) {
+echo __LINE__, ' - in INTL_IDNA_VARIANT_2003 condition', PHP_EOL;
                     //Fall back to this old, deprecated/removed encoding
                     $punycode = idn_to_ascii($domain, $errorcode, \INTL_IDNA_VARIANT_2003);
                 } else {
+echo __LINE__, ' - in fallback condition', PHP_EOL;
                     //Fall back to a default we don't know about
                     $punycode = idn_to_ascii($domain, $errorcode);
                 }
                 if (false !== $punycode) {
+echo __LINE__, ' - returning based on punycode not false', PHP_EOL;
                     return substr($address, 0, $pos) . $punycode;
                 }
             }
         }
 
+echo __LINE__, ' - fall back return', PHP_EOL;
         return $address;
     }