There is a bug in that plugin but you can install “Hotlink Image Cacher with Keyword” and run it once. All QR codes will now be linked to your upload directory!
just to add to your coding, you need to open the file smtp.php-class, class-phpmailer.php, pluggable.php and change some settings, the same ones you mentioned but each item must be in those files where it was written!
There is no setting for SMTP in the wordpress admin. Unfortunately, they left that part for users to encode themself. Probably because it is understood that each server on which the WP is installed have its own sendmail (usr / bin / sendmail) on localhost. But, there is lot of plugins that solve this mistery 😉
