Emails are rejected with a Base64 error

Error

Emails are rejected by NoSpamProxy even though the Level of Trust filter has marked them as trusted. The following error message is displayed in message tracking and NDRs:

A part of the email could not be decoded. System.formatException: Invalid character in a Base-64 string.

The following error message is displayed in the message tracking:

The Base64 encoded content was invalid.

Status

The problem with the email in question is due to the security check by NoSpamProxy. NoSpamProxy detects a conflict with the RFCs in the body. The email does not have proper Base64 encoding and will be rejected. This security check can only be switched off in the configuration file of NoSpamProxy.

Version 7.x and 8.x

Alternatively or additionally you have the possibility of a repair attempt by NoSpamProxy. In this case, NoSpamProxy will try to ignore the superfluous characters or fill in missing characters to obtain a valid encoding. This does not always work, but can be helpful.

  1. Go to ..\nospamproxy\AntiSpam Role\config in the program directory.
  2. Open the file antispamrole.config.

    NOTE: You cannot save the file until the NoSpamProxy service is stopped. Otherwise, the change is discarded.


  3. Search the file for the following line: </netatwork
    .nospamproxy.proxyconfiguration>
  4. Insert the following key directly above this line:
    <encodingOptions invalidBase64LengthHandling="IgnoreExtraCharacters" />
  5. Save the file.
  6. Restart the NoSpamProxy service.

From version 9x

  1. Go to C:\ProgramData\Net at Work Mail Gateway\Configuration.
  2. Open the file Gateway Role.config.

    NOTE: You cannot save the file until the Gateway Role has stopped. Otherwise, the change is discarded. The change must be made on all Gateway Roles.

  3. Search the file for the following line:
    </netatwork.nospamproxy.proxyconfiguration>
  4. Insert the following key directly above this line:
    <encodingOptionsinvalidBase64LengthHandling="IgnoreExtraCharacters" />
  5. Save the file
  6. Restart the Gateway Role.

NOTE: To benefit from the better coding, you must install the latest version of NoSpamProxy.