Email addresses using special characters (specifically email addresses with a + as part of the local address) are not being correctly encoded in the request to Kickbox.
According to the RFC, valid characters in the local address include:
!#$%&'*+-/=?^_`{|}~
Based on the code in UrlHelper.cs, it looks like the email value is not URI escaped when building the request
return string.Join("&",
properties.Select(x =>
string.Concat(Uri.EscapeDataString(x.Key), "=", x.Value.ToString())));
This can be reproduced by a request similar to the following:

The value for "Email" is not coming back as sent in the request, and the kickbox Result does not agree with what Kickbox would reply

Email addresses using special characters (specifically email addresses with a + as part of the local address) are not being correctly encoded in the request to Kickbox.
According to the RFC, valid characters in the local address include:
!#$%&'*+-/=?^_`{|}~
Based on the code in UrlHelper.cs, it looks like the email value is not URI escaped when building the request
This can be reproduced by a request similar to the following:
The value for "Email" is not coming back as sent in the request, and the kickbox Result does not agree with what Kickbox would reply