Mein Unternehmenskonto
The extended mailbox

To enable companies nationwide to process applications simply, quickly and without media discontinuity, the federal government has decided to create a standardized Unternehmenskonto as part of the implementation of the Online Access Act (OZG). This is intended to facilitate access to digital administrative services via a central platform for contact with public authorities.

In its circular resolution of February 14, 2020, the IT Planning Council instructed the states of Bremen and Bavaria to roll out the uniform Unternehmenskonto they had designed for all the states. The Unternehmenskonto consists of a building block principle;

  • Bavaria is creating the technical and practical prerequisites for implementation on an ELSTER basis (modules 1-4);
  • Bremen designs the components of an extended company mailbox and authorization as independently usable convenience functions in the company account in coordination with Bavaria (modules 5-6).

Based on the ELSTER technology from Bavaria, which is already established in the tax sector, a central online portal with the standardized company account - My Company Account (Mein.UK) - is offered.

In addition to the already existing and well-known "ELSTER mailbox", Bremen contributes an extended mailbox as well as the necessary authorization mechanisms.

Both functionalities were requested in particular by representatives and associations from the business community. Bremen relies on the expertise of its IT service providers and has commissioned Dataport with the implementation of authorization control and Governikus with the implementation of the extended company mailbox(OZG-PLUS mailbox). This includes the modules for business and government (MuWiSta), which consist of modules 5 + 6 of the standardized company account. The extended company mailbox also enables companies to participate in electronic legal transactions - i.e. judicial communication.

Both the company mailbox and the authorization control system developed by Dataport have been available for productive use throughout Germany since July 2023.

Convenient and legally binding communication with authorities and the judiciary for companies

The unified Unternehmenskonto is designed to facilitate access to administrative services, in line with the OZG. Companies can easily set up and configure their extended company mailbox with their ELSTER organization certificate.

The MuWiSta - modules 5 and 6 provide solutions for written form substitution communication for organizations. The "module 5" developed by us - the so-called OZG-PLUS-Postfach - offers extended mailbox functionalities in Unternehmenskonto.

We are therefore pursuing two overarching goals with the OZG-PLUS mailbox:

  1. A service that standardizes communication between administration and organizations. In this context, unification means the similar way of accessing and sending messages and not the unification of the respective infrastructures.
  2. Creating a bridge between the respective infrastructures and at the same time a unified approach so that further domain-specific approaches become unnecessary.

The 6 building blocks at a glance

Unternehmenskonto Building Blocks


Two women and a man discuss

Functionalities of the extended company mailbox (OZG-PLUS mailbox) - Module 5

The OZG-PLUS mailbox enables communication with a wide range of administrative authorities and bundles these in an end-to-end encrypted web application for structured data transmission.

  • Communication can be initiated both by the company (application) and by the administration. Depending on the scenario, responses can be sent to incoming messages or notifications via the OZG-PLUS mailbox.
  • The OZG-PLUS mailbox enables legally binding delivery.
  • The provision of functional mailboxes offers the possibility of enabling several employees of the organizations to access the notifications and messages in (functional) mailboxes
  • End-to-end encryption without sharing key material.
  • Provision of freely configurable substitution rules (temporary, permanent), which can also be used to prevent damage in the event of the death or departure of employees.
  • Support and mapping of more complex company structures through "function mailboxes" that can be configured according to individual requirements



November 2021

Commissioning of the MUWISTA project

Bremen commissions Dataport and Governikus to implement the MUWISTA (Modules for Economy and State) project, which includes modules 5 and 6 in Unternehmenskonto.

To the press release

Q2 2023

Public piloting

July 2023

Go Live with basic functions

Q4 2023

Release MJP

Natural persons can use legally binding, electronic legal transactions via a BundID account.

To the press release

Q1 2024

Provision of extended mailbox functionalities

Multiple function mailboxes and member management with substitution rules per company possible.

To the press release

Q2 2024

Multiple admins

Q3 2024

News search and filtering

Answers to frequently asked questions (FAQ)

The "Administration" role in the OZG-PLUS mailbox essentially has the following two areas of responsibility:

1. administration of functional mailboxes
- Create
- Rename
- Delete
2. administration of members in the function mailboxes
- Adding new members and substitutes
- Removing existing members and representatives

At the beginning, an employee of the company can take on the "Administration" role. This first admin can then assign the role of "Administration" to other employees in order to ensure that this role is representative and failsafe, even for technical administration.
Yes, it is possible to set up several functional mailboxes for a company. These are managed by specialist admins, who you as a company determine by issuing the ELSTER organization certificates. The admins can add employees to a function mailbox or remove them from a function mailbox so that employees can be members of several function mailboxes of the company.
The administrator can add several employees to a functional mailbox as users. Members of a functional mailbox can represent each other, they can decrypt and read messages that have already been received as well as messages received in the future using their personal key material.
As part of the connection of the mailboxes by the administration, the online service must enable the selection of delivery to the P.O. Box 2.0 and the OZG-PLUS P.O. Box. When selecting the OZG-PLUS mailbox, the online service must determine the company's existing functional mailboxes and offer them to the applicant as delivery points for selection. The OZG-PLUS mailbox has a corresponding directory service for this purpose.
By making a selection, the employee from the company can decide exactly where delivery should take place.
Yes, the messages are end-to-end encrypted. The end side for end-to-end encryption of the message is the specialist procedure, the other end side for end-to-end decryption is the specific individual person from the company with their personal key material. The private key for the user is created exclusively on the client side in the browser, is never transferred to the server and remains locally with the user. The provision of the private key in the decryption dialog also takes place entirely in the browser.

Each member of a function mailbox decrypts the message in the function mailbox with their own personal private key.

End-to-end encryption means that each recipient is responsible for checking attachments for viruses, as the system cannot see the content of the message.
The SDK is provided via a public repository, the SKD is currently available as a Java library.

For more information, please refer to the integration guide. You can find it in the download area below.
The total size per message and the number of attachments per message are currently not limited; a single attachment can currently be up to 50 MB in size. There are no technical limitations to the formats; the standard formats are PDF and XML.
The IT Planning Council has made a decision in favor of two mailboxes. The choice of which mailbox to use should be left to the end user. As things stand, it is therefore necessary to connect both mailboxes. In the future, the mailboxes will be merged into one central mailbox.
The difference between P.O. Box 2.0 and the OZG-PLUS P.O. Box is that P.O. Box 2.0 represents a personal employee P.O. Box due to the 1:1 relationship between the ELSTER organization certificate and the P.O. Box, while the OZG-PLUS P.O. Box offers the possibility of enabling several employees of the organizations to access the notifications and messages in (functional) P.O. Boxes and thus also very easily depicts substitution regulations.
Mailbox 2.0:

- No setup necessary, supplied when applying for the ELSTER organization certificate
- The 1:1 relationship between the ELSTER organization certificate and the mailbox makes it a personal employee mailbox
- Added value, especially for less complex company structures

OZG-PLUS mailbox:

- Freely configurable functional mailboxes are supported, and deputy rules (temporary, permanent) can also be set up.
- End-to-end encryption without sharing key material
- Support and mapping of more complex company structures
This is the case according to the Online Access Act (OZG).

The IT Planning Council has made a decision in favor of two mailboxes. The choice of which mailbox to use should be left to the end user. As things currently stand, it is therefore necessary to connect both mailboxes. In the future, the mailboxes will be merged into one central mailbox.

Your question could not be answered?

For additional information, please visit the FAQ on the My Company Account website.

You want to be a pilot?

For a pilot request to connect specialized procedures to the transport route interface for the OZG-PLUS-Postfach, please fill out the following contact form:

Phone number

Phone number


Integration Guide
Integration guide for linking the OZG-PLUS-Postfach to existing specialist procedures
Specification base
Basic specification for service responses of the OZGPP specialized procedures Service API
Specification mailbox directory query
Specification for the mailbox directory query of the OZGPP Fachverfahren Service API
Specification transfer
Transfer specification of the OZGPP Fachverfahren Service API based on Elster Transfer 3.3.0
SDK Release Notes
SDK Release Notes Version 2.1.0
OZG-PLUS mailbox release notes
OZG-PLUS mailbox Release Notes Version 1.3.0

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