This article provides an overview of the minimum requirements that must be met in order to run NoSpamProxy.

Note: In order for you to receive support services,

  • the listed requirements must be fulfilled and
  • a corresponding manufacturer support contract must be in effect.

We do not guarantee the completeness of the following information on third-party products. In any case, make sure to check the manufacturer’s pages for updates!

General requirements

  • A corporate email server, either in the company network or in the cloud.
  • NoSpamProxy can NOT be operated using the combination “Domain Controller + Exchange + NoSpamProxy” on one single system, because the operation of Exchange on a domain controller is prohibited. See Exchange Server Supportability Matrix.
  • NoSpamProxy can be installed on a system in parallel with the email server. However, this combination is not recommended, because of duplicate port assignments (mostly ports 25, 443 and 6060/6061), which can cause problems during operation. We recommend to always change the ports of the email server in case of parallel operation, so that NoSpamProxy can be reached from outside via the standard ports.

NoSpamProxy uses the following standard ports:

  • Port 6060/6061 TCP
    • internal communication between the Intranet Role and the Gateway Roles
  • Port 25 TCP
    • SMTP
    • inbound and outbound
    • modifyable
    • also used by Exchange during parallel operation
  • Port 443 TCP
    • SSL
    • internal and external communication with the Web Portal
    • modifyable
  • Port 465 TCP
    • POP3
    • to retrieve POP3 messages
    • no support for NoSpamProxy Protection

Hardware requirements

The following specifications are minimum requirements. The recommended configuration depends on the email volume and the use of individual NoSpamProxy functions.

  • 4GB RAM
  • 2 processor cores
    • virtualized or physical
  • Hard disk space
    • should be discussed individually with the support or presales team
    • If Intranet and Gateway Role are operated on one single system with no Web Portal present, 100GB should be sufficient.

Supported NoSpamProxy versions

The following versions are currently covered by our support:

  • Version 13.2
  • Version 13.1
  • Version 13.0
  • Version 12.2
  • Version 12.1 (no longer supported with release of version 14)
  • Version 12.0 (no longer supported with release of version 14)
  • Version 11.1 (no longer supported with release of version 14)

NoSpamProxy Outlook Add-In

  • Outlook 2010 and later

Microsoft Operating Systems

  • Microsoft Windows Server 2019
  • Microsoft Windows Server 2016
  • Microsoft Windows Server 2012 R2
  • Microsoft Windows Server 2012 (no longer supported with version 14)
  • Microsoft Windows Server 2008 R2 (no longer supported with version 14)

Microsoft .NET Framework

  • .NET Framework 4.8, supported as of NoSpamProxy version 13, mandatory as of version 14
  • .NET Framework 4.7.2, mandatory supported from NoSpamProxy 12.2 onwards
  • .NET Framework 4.6.2, supported up to version 12.1 and older
  • .NET Framework 4.5.7, supported up to version 11.1 and older

Microsoft SQL Server Express Version

  • Microsoft SQL Server 2019 Express Version (supported for Windows Server 2016 and above)
  • Microsoft SQL Server 2017 Express Version (supported for Windows Server 2012 R2 and Windows Server 2016)
  • Microsoft SQL Server 2014 Express Version (no longer supported with version 14)
  • Microsoft SQL Server 2012 Express Version (no longer supported with version 14)
  • Microsoft SQL Server 2008 R2 Express Version (no longer supported with version 14)

For details on supported combinations, please refer to the official Microsoft pages for each product.

Microsoft SQL-Server Standard/Enterprise

  • Microsoft SQL-Server 2012 SP4 and later
  • Microsoft SQL-Server 2012 SP3 and older (no longer supported with version 14)

Microsoft Report Viewer

Microsoft Report Viewer 2010 is required to install the Intranet Role.

Microsoft Visual Studio Tools for Office

Visual Studio Tools for Office 2010 Runtime or higher is required to install the Outlook Add-In.

Further notes

  • Make sure that any third-party applications you use that connect to NoSpamProxy are covered by their respective manufacturer’s support. If this is not the case, the NoSpamProxy support team will not be able to provide support.
  • Make sure that the necessary exceptions are set in the local Windows Defender (and other AV scanners used) to allow NoSpamProxy to run smoothly.
  • If you have installed NoSpamProxy and Microsoft Exchange on the same server, make sure that the respective version of the framework is supported by Exchange before installing or updating the Microsoft .NET framework. An overview of supported versions is provided in the Exchange Server Supportability Matrix.
  • Further details about the installation of the add-in can be found in the Outlook Add-In Installation and Group Policy manual. There, the installation with the MSI file for software distributions is also addressed.


The Cyren IP Reputation filter is available if NoSpamProxy Protection is licensed. This filter performs the check of the IP address of the sending system, classifies it according to the classification received from Cyren and assigns corresponding SCL points:

  • No known risk (0 SCL points)
  • Medium risk (1 SCL points)
  • High risk (3 SCL points)

Depending on the setting of the evaluation criteria and additional classifications of the other filters in the applied rule, an IP address can thus lead to the rejection of the emails. This rejection can already take place during the envelope phase, so that further information – for example, the subject – is no longer transmitted.

NoSpamProxy has no influence on these evaluations. However, every affected sender can have their IP address and its classification checked and adjusted via the Cyren support page.

Further information



The Cyren Premium AntiVirus scanner is part of the Malware Scanner action and can be used if NoSpamProxy Protection is licensed. Cyren Premium AntiVirus checks attachments that are attached to an email. In doing so, it carries out two basic checks:

  • Local checks against definitions
    • The definitions are regularly downloaded from the Cyren servers. In case of access problems to the Cyren servers, the definitions must not be older than two days.
    • During the check, the attachment is placed in the directory C:\ProgramData\Net at Work Mail Gateway\Cyren\Temp, checked and deleted again.
  • Live checks – Zero Hour Protection
    • Check for conspicuous attachments in the recent past. A hash value is generated and sent to Cyren, which then sends a response with the corresponding classification by Cyren.

Unlike with the Cyren AntiSpam filter, the NoSpamProxy support has no way of influencing this behaviour in the case of a misclassification.
In the case of misclassifications – i.e. false positives or false negatives – the sender or the recipient of the email must always contact Cyren and have this corrected accordingly.

A description of the process can be found on the respective Cyren support page.

In case of local problems or missing definitions, please refer to the Knowledge Base article Cyren Engines – Troubleshooting


To ensure parallel operation with other locally installed virus scanners on the gateway role, please refer to the Knowledge Base article How to configure on-access virus scanners and define the exceptions as described!

Further information


Below you will find information on using the Sandbox Service in NoSpamProxy. For general information on how a cloud sandbox works, licensing or data protection, see Informationen zum NoSpamProxy Sandbox-Service (German only).


Since 2018, we strongly recommend NoSpamProxy customers to take a whitelisting approach to content filtering (see our article on email firewalls). This recommendation applies in particular to the use of the NoSpamProxy Sandbox service.

An example: Even if an “executable file for Windows” is supported by the sandbox, the question arises whether one wants to allow this potentially dangerous file type for one’s own company at all. In this case, it makes more sense to generally reject this file type and thus also save the upload to the sandbox.

If a file is classified as unsuspicious by the sandbox service, the respective email will be delivered.


Sandbox hash query

The retrieval of the hash values from the sandbox database can be carried out without restriction and without deduction of purchased licences. For this purpose, the corresponding check mark Query the sandbox if the attachments of inbound emails are known to be malicious must be ticked.

NoSpamProxy Sandbox Service - Hash Check
This check can be applied to all file types.

Sandbox upload

File uploads are limited to 20 files per user and month.

This value is the total value of permitted uploads; there is no strict user check. This means, for example, for a 50-user licence that the respective NoSpamProxy installation may upload 1000 files to the sandbox in one month. Costs may be incurred if the limit is exceeded.

To limit the sandbox check to individual file types, an additional content filter action should be created that is only applied to certain file types.
To enable uploading, the option Upload unknown files to the sandbox for analysis must be activated.
NoSpamProxy Sandbox Service - Hash Check an Upload

Supported file types

  • Executable files
    • Executable files for Windows
  • Office – Word
    • <all>
  • Office – Excel
    • <all>
  • Office – PowerPoint
    • <all>
  • Video
    • Adobe Flash (SWF)
    • Adobe Flash Video (FLV)
  • Text
    • Rich Text Format
    • Rich Text Format with OLE objects
    • PDF
    • PDF with URLs
  • Archives and compressed files
    • ZIP-compressed file
    • GZIP-compressed file
    • TAR archive
    • GZIP-compressed TAR archive
    • 7Zip-compressed file
  • Scripts (Configuration via file names)
    • .js
    • .vbs
    • .wsf
    • .ps
    • .py
    • .hta
    • .perl
    • .php
    • .sh

Delivery delay

If a file has to be uploaded to the sandbox (sandbox upload), the email will not be accepted initially and temporarily rejected so that the sending email server delivers it again.

The temporary rejection is applied here because the analysis on the sandbox array takes a certain amount of time, but should be completed after a regular 5 minutes when a new delivery attempt is made.

This will result in a delivery delay for the respective emails which must be taken into account accordingly. We therefore recommend that you check exactly which files should really be sent to the sandbox. Note the following option if time-critical processes or mailboxes exist in your company:

  • Is a sandbox hash query sufficient instead of a complete analysis (sandbox upload)?
  • It is possible to create different actions in the content filter to configure different actions for a content filter entry for “Trusted emails” and “Untrusted emails” between a sandbox upload and a sandbox hash query.
  • Office documents can be converted into a secure PDF document by NoSpamProxy Content Disarming if necessary.