I am getting below error in magento 2 local system.
We're sorry, an error has occurred while generating this email.
php bin/magento deploy:mode:set developer
php bin/magento cache:flush
Error filtering template: Unable to write file into directory \C:/xampp/htdocs/Magento/pub/media/catalog/product\cache\f073062f50e48eb0f0998593e568d857/m/b. Access forbidden.
The first thing you need to do is go to your .htaccess file. Uncomment
SetEnv MAGE_MODE developer
The error message is 90% of the time misleading and most likely you have an xml parsing issue. Either way turning on the developer environment and clearing the cache will pull the error.
Without seeing your error log it'd be hard to give an exact diagnosis. Some users will say sendmail will fix this error but generally this is because the error is trying to be emailed to you and that is because you are not in the correct developing environment to debug the issue. This could be because you are in default or production mode which is not ideal for fixing issue.
The sendmail module is meant to allow a site to operate and if any issues do occur with the site then the developer can be notified and hopefully the error hasn't caused a full site rendering issue. This way a site can still operate unbeknown to users and the issue can be resolved by a qualified developer behind the scenes.