Invoicely project

I joined the Invoicely project while being part of the Stack Holdings GmbH development team. During this brief but exciting period, I contributed to migrating Email delivery and improving stability, introducing bounce and complaints handling mechanisms, successfully conceptualizing and implementing security protection against automated modulating spam attacks, and Zendesk integration.

Interesting topics

Email delivery improvements and quality control

I was invited to this project because of my previous experience in email delivery and proven track record on eversign email delivery project.

Invoicely had many customers generating massive amounts of invoices and documents. Email delivery was the key communication route at the time. Sometimes, emails from various customers would bounce or end up with spam or fraud complaints. We designed and implemented a system that tracks records and evaluates the quality of emails sent by each of the Invoicely customers independently. Furthermore, we engineered a system capable of automatically tracking, flagging, and blocking problematic user accounts.

Although I will not discuss technical details and rules of email delivery control, I can comment on the results. In a short time, we recognized many culprits, which were sending out spam emails, significantly improved IP reputation for our delivery emails IP addresses and overall email delivery quality. As a result, we managed email delivery risk much better, and we had data to make informative decisions.

The project was a complete success, and we extended it into building an automated anti-spam and fraud protection system.

Automated anti-spam and fraud protection

This project was an extension of email delivery improvements and quality control project. In short, we conceptualized, designed, and implemented a mechanism for monitoring account activity to detect automated spam and fraudulent accounts, flagging or blocking them altogether. Project results were fantastic; our response rate to noticing spam-generating and fraudulent user accounts increased to 80-90%.

Integration between Invoicely and Zendesk notifications

I was invited to this project because of my previous experiences integrating products with Zendesk, such as eversign-Zendesk and ZeroSSL-Zendesk integrations. In short, we implemented already proven designs to enable customer success teams to deliver important Zendesk notifications to all Invoicely customers in time. As a result, end-user communication significantly improved, and the Invoicely customer support team received fewer tickets and complaints.

Designing, implementing, and evaluating KPIs for Invoicely with company CFO

After successfully implementing the KPI framework for eversign and ZeroSSL products, we also decided to extend this project to Invoicely. This project was a fantastic experience because it showed how good initiative and applicable technical delivery quickly find a way to the other products within the company. I won’t go into KPI details here, but I will state that implementing KPIs for Invoicely gave us much-needed clarity on growth and user base. In addition, it increased our ability to make informed data-driven decisions.


Invoicely is an online invoicing for small and medium-size businesses. This product enables customers to create and deliver invoices and estimates, track time and expenses and accept online payments.

My roles: Senior Software Engineer

Impact: New features; Improved Security; Improved Scalability; Email delivery; Spam protection; Zendesk integration