Invoicing customer is certainly the riskiest touchpoint in your user journey. Every bill is a monthly reminder for your users that they're giving you money.

And if you think that nobody opens them, think again: open rates on transactional emails are four to eight times higher than other emails.

Invoice emails are tricky, ok. But they also are a great opportunity to remind users of how valuable your product is. You can use them to talk about you new features and improvements, share your roadmap, showcase case studies and testimonials. It's also a good channel to ask for feedback and offer your help.

Sending bills doesn't to be painful. It can be something your users will look for every month, just like they do for a newsletter.