SUCCESS STORY

Built to withstand tax season: how Buhl Data delivers 68 million emails safely in just 4 months

How Buhl Data Service GmbH runs its user communications reliably and at scale with Brevo.

~98,76% runs its user communications reliably and at scale with Brevo.
~30 % open rate for transactional emails
0,1 % unsubscribe rate at up to 23 million emails/month

About Buhl

Buhl Data Service GmbH has supported millions of private individuals, freelancers, and businesses across German-speaking countries with their tax and financial affairs since 1986. With WISO Steuer, Buhl is also the market leader for tax software in Germany.

With products like WISO Steuer, WISO Mein Büro, and Finanzblick, the company has become the default choice for millions of users navigating tax and financial questions. Those users expect timely, dependable updates on product releases, tax deadlines, and account activity, especially during tax season, when sending volume spikes sharply in a short window.

The challenge: growing user numbers, growing expectations

Buhl runs a portfolio of apps serving different audiences, including WISO Steuer, finanzblick, and MeinVerein. Customer communications used to run on a complex, heavily IT-dependent in-house system: every change tied up valuable developer resources and limited how independently individual teams could work. As the user base kept growing, that setup hit its limits.

Three key hurdles to scaling

Fragmented account structure : teams like the tax product team needed higher sending volumes and more advanced features, but operated separately from the main account with no shared contract.

Strict data separation: the different product teams (tax, finance, and association) needed to communicate independently, but data protection rules meant they couldn't share a single marketing environment.

Seasonal volume spikes: sending volumes surged during tax season, putting deliverability under pressure, since emails still had to arrive reliably even at peak load.

The solution: one platform, three independent environments

Since June 2025, Buhl Data Service has used Brevo to handle all of its customer communications reliably while keeping clear data separation between product areas. That replaced its previous in-house systems, and the company now runs its marketing independently, without ongoing reliance on IT.

Consolidation under one shared contract

Each product team, tax, finance, and association (MeinVerein), gets a fully self-contained environment with dedicated access. No separate contract required.