@Jun3 I have been looking for something similar and have come across more people asking for the feature since 2017. My suggestion is to use xero.com. There you are able to customize your email templates with variables like month, customer and other data rather than following the suggestion they offered here which is basically to create and email template for every customer for every month which is pretty stupid. Any lesser known company could what you are asking in the blink of an eye and this people have seen this feature requested for years now. My guess is they will never add that feature.