From Braze to Reteno: Million-Scale Sending in Under 3 Weeks

After a previous platform migration had taken approximately four to six months, this consumer app wanted a clearer path out of Braze. It needed a partner that understood mobile apps, could preserve complex messaging logic, and could support millions of email sends each month.

Reteno started with a live proof of concept that required no development work from the client. Its specialists then migrated the messaging setup and managed a controlled sending ramp-up. Following the move, the app returned to its usual sending volumes in under three weeks.

Migration Highlights

• Under 3 weeks — to return to usual sending volumes during the sending ramp-up.
• Up to 2M emails in a day — the client’s peak sending scale, alongside millions of monthly sends.
• 0 client development work — required for the live proof of concept.

Company

The company operates a consumer mobile app and uses email and mobile push to communicate with its audience. Its messaging program includes dynamic email content, audience segments, and complex automated journeys.

With millions of email sends each month and peak daily volumes reaching up to two million, the company needed both the required messaging functionality and a practical plan for moving its operations to a new platform.

Challenge

Finding the right balance of cost, app expertise, and migration support

Cost was an important reason for considering a move from Braze, but it was not the only factor. The customer explicitly valued Reteno’s focus on mobile apps and saw that expertise as an advantage for its team.

The customer also wanted confidence in how the transition would be delivered. In its previous migration to Braze, the team had expected more help but had ended up rebuilding every email. According to the customer, that project took approximately four to six months.

With a new deadline approaching, the team needed to see how its existing communications would work in Reteno before allocating engineering resources to another full migration.

Preserving the behavior behind emails and journeys

The existing setup could not be moved by copying designs and text alone. Dynamic emails contained conditions that determined which content each recipient saw. Automated workflows depended on communication rules that also needed to work correctly in Reteno.

The task was to preserve the required behavior while adapting its implementation to a different platform. At the same time, the sending transition needed to accommodate the client’s established volumes and preparation for a major promotional campaign.

Solution

1. A live proof of concept without client development work

Before committing to the broader migration, the client wanted to test one existing Braze workflow in Reteno with real users. Together, the teams selected the workflow and agreed on the share of its audience that would receive communications through Reteno.

Reteno’s specialists recreated the workflow, including the relevant email content, personalization rules, and contact data needed for that scenario.

To run the test without changes to the client’s app or backend, Reteno added blocks and webhooks to the existing Braze workflow. These created contacts in Reteno and passed the attributes and onboarding events required to trigger the selected communications.

The agreed share of users could therefore receive the workflow’s emails through Reteno while the existing Braze setup continued to serve the remaining audience.

The client could evaluate the actual communication logic and personalization before investing in full integration. Its involvement in the pilot was limited to agreeing on the scenario and audience share; Reteno handled the technical implementation on both platforms.

Early customer feedback described open rates as comparable. The pilot provided practical evidence that the selected scenario could run in Reteno; it was not presented as proof of a performance uplift.

2. Hands-on migration of emails, personalization, and workflows

After the proof of concept, Reteno’s migration team transferred the email designs and copy and adapted the underlying personalization using Velocity.

The work included rebuilding conditions that selected the appropriate content and profile values for each recipient. This preserved the required dynamic email behavior through an implementation suited to Reteno.

The team also recreated audience segments and automated communication workflows. For complex scenarios, it refined the logic so that the journeys would operate according to their original intent.

Adapting these rules accounted for a substantial share of Reteno’s work. The team’s responsibility covered the functioning messaging setup, alongside its visible content.

3. A clear division of responsibilities for the full migration

The proof of concept required no client development work. The broader migration did require the client’s engineering team: it handled SDK integration, event configuration, app and backend changes, data cleanup, and attribute backfills, as well as testing and approvals.

Reteno handled email migration, personalization adaptation, workflow recreation, segment migration, and support throughout the transition. This kept the client from having to rebuild its messaging assets internally while recognizing the engineering work required within its own systems.

4. A controlled ramp-up to established sending volumes

The transition also included preparing email sending capacity for the client’s established scale and an upcoming major promotion.

Reteno’s deliverability team planned provider-specific sending batches, increased throughput, and monitored the ramp-up. This gave the move a defined sending plan alongside the migration of templates, data, and workflows.

Following the move, the company returned to its usual sending volumes in under three weeks. This describes the sending ramp-up, rather than the duration of the pilot or the entire migration project.

Results

Million-scale sending running through Reteno

The company moved its email and mobile push communications from Braze to Reteno. Its email program operates at millions of sends per month, with a peak daily sending scale of up to two million emails.

The sending ramp-up brought the client back to its usual volumes in under three weeks. The peak daily figure describes the client’s sending scale; it is not a claim that two million messages were delivered in a particular Reteno campaign.

A working pilot before full integration

The customer tested an existing workflow with real users before committing internal development resources to the broader migration. Reteno implemented the pilot without requiring changes to the client’s app or backend.

Required personalization preserved and workflow logic refined

Reteno adapted complex dynamic email logic using Velocity and recreated the company’s automated journeys and segments. Workflow adjustments supported the intended communication behavior in the new platform.

A more manageable transition for the client

Reteno took on the messaging migration and deliverability ramp-up, while the client focused on the engineering, data preparation, testing, and approvals needed on its side.

According to feedback shared with Reteno’s team, the customer found the transition easier than expected after its previous migration experience.

Why This Matters for You

Moving a mature messaging program requires a plan for the content, logic, data, and sending volumes that your business already depends on.

This case shows how a live pilot and hands-on migration support can make that work more manageable:

✅ Test an existing journey with real users. Evaluate the required communication behavior before committing to full integration.

✅Preserve the personalization you need. Adapt the conditions behind dynamic content alongside email designs and copy.

✅Define the work on both sides. Establish which tasks the migration team will own and where your engineers and marketers need to contribute.

✅Plan for your actual sending scale. Include provider-specific ramp-up and deliverability monitoring in the transition.

✅Choose relevant expertise alongside price. Assess whether the team understands your app’s messaging requirements and can explain how it will support the move.

Considering a move from Braze? Book a Reteno demo to discuss a proof of concept, your existing messaging logic, and a migration plan for your sending volumes.