Dear Software Partner,

We would like to highlight the recommended and supported way to send files when using our Massprinting (Payslip) API:

While our API continues to function as before, we have noticed that some older integrations may still be sending files as Base64-encoded strings in query parameters or JSON. This method is not optimal and may lead to issues with file size limits, encoding errors, or general reliability.

To ensure stable and correct handling of documents, file uploads should be done using multipart/form-data, which is the expected and fully supported format.

What You Should Do?

Please check your integration and update it to use multipart uploads if you're currently sending Base64-encoded content.

Why Does This Matters?

Using multipart/form-data ensures:

• Faster processing

• Reduced risk of delivery errors

• Better support for larger files

• Cleaner separation between file and metadata

• Improved long-term compatibility with our platform

If your integration already uses multipart uploads, no action is needed.

What is the Mass Printing Service?

Maventa’s Mass Printing Service allows you to send PDF files as letters through a printing service in Finland. Originally designed for delivering payslips, the service can be used to send all types of letters, as long as the printing service requirements are met (for example, placing the recipient’s address in the correct position on the PDF document). The service is well suited for sending announcements, meeting invitations, or direct payment notifications — both domestically and abroad.

You can find more information about the service on Maventa’s help pages and in the integration documentation.

If you have any questions or need help updating your implementation, we’re here to support you.

Best wishes,

Maventa customer care