Recently, we implemented an

integration with Free Mobile

, the French mobile operator, for one of our clients. Free Mobile communicates with its partners through the SMPP protocol, which is widely used in telecom for exchanging SMS messages.

This wasn’t our first experience working with SMPP. We had already completed several similar integrations in the past - including projects with other operators and aggregators such as HighCo - so the team was able to move quickly and anticipate most of the tricky parts of the protocol.

Sometimes Legacy Wins: Implementing UCP for SMS

Though UCP (Universal Computer Protocol) is considered a legacy protocol for sending SMS, there are still cases - especially with European mobile operators - where you're required to comply with it.

In one of our projects, we had to implement UCP ourselves, as no actively maintained Java libraries were available. Fortunately, UCP is a text-based protocol, which makes it relatively simple to work with — but only if you handle the details precisely.

A typical UCP message looks like this:

02/51/O/51/username/password/123456/0044170000000/Hello World//////////1/7

The trick? Carefully follow the specific field formats, character escaping rules, and checksum logic. When implemented properly, UCP still gets the job done - even in a modern system.

In our journey to optimize email delivery, we've integrated various email services into our products. I would like to highlight two of them - SendGrid and Mailjet. Here's a breakdown of our findings, enriched by the broader developer community's experiences

SendGrid: Powerhouse for Enterprise-Level Needs

Robust Integrations: Seamlessly integrates with major cloud providers like AWS, Azure, and Google Cloud Platform, facilitating scalable and reliable email solutions.
SendGrid.

Advanced Features: Offers detailed analytics, dynamic templates, and a suite of delivery and reputation tools, making it ideal for high-volume transactional emails.

Mailjet: Streamlined Solution for Agile Projects

Efficient Monitoring: Provides real-time analytics on email deliverability and engagement, allowing for quick adjustments to campaigns.
Mailjet

Strict Compliance: Mailjet's sensitive monitoring can lead to account blocks at signs of misuse, which, while ensuring high deliverability standards, may pose challenges for some users.

Both SendGrid and Mailjet are reliable email service providers, each excelling in different areas:

• Choose SendGrid for enterprise-scale applications requiring advanced features and integrations.
• Opt for Mailjet for smaller, agile projects that benefit from a user-friendly interface and straightforward setup.

In designing our Buy Now, Pay Later (BNPL) solution for the Swiss market, we included a critical step: managing unpaid invoices.

Traditionally, forwarding overdue invoices to debt collection agencies required manual paperwork - a process that was slow, expensive, and error-prone.

To modernize this, we built a direct API integration with leading

Swiss debt collection providers

This integration delivered:

• Fully automated invoice handover
• Lower operational costs
• Faster, more reliable collections
• A scalable fintech workflow

Result: A debt collection process that is faster, cheaper, and seamlessly embedded into our BNPL platform - setting a new standard for Swiss fintech solutions.