Is it possible to exceed the 999 character limit on setting an InternetHeader in an Addin for Outlook?

Question

For a business project, I am creating an Outlook Addin which will decode an email and check signatures after which we then add labels and so on.

This has to be compliant with the NATO standard STANAG 4774 & 4778.2:
https://nso.nato.int/nso/nsdd/main/standards/srd-details/197/EN

https://nso.nato.int/nso/nsdd/main/standards/stanag-details/8612/EN

To be compliant with these standards, I am required to send an InternetHeader with my email this way:

 item.internetHeaders.setAsync({ "Binding-Data": result }, (setHeaderResult) => {
        if (setHeaderResult.status == Office.AsyncResultStatus.Succeeded) {
          item.saveAsync(result => {
            console.log(result.value);
          })
        }
        else {
          console.log(setHeaderResult);
        }
      })

However, my header will exceed the 999 character limit in most of the cases.
Because of this limit, the header does not want to be added to the email, resulting in an error:

"Sys.ArgumentOutOfRangeException: Sys.ArgumentOutOfRangeException: Specified argument was out of the range of valid values.
Parameter name: Binding-Data"

However, I know it is possible to send an email with larger headers.
To test and verify this, I've created a powershell script that sends an email with my required data in the header, which goes perfectly fine, and it's possible to be read out using the Javascript API in the Addin.

I was wondering if there is the possibility to increase or disable the max character limit in the API/Addin, or if it's possible to ask a feature request for this.

Answer 1

This is a limit defined by the RFC5322 standard. Each line is limited to 998 or less characters and should be no more than 78 characters.

The fact that you were able to receive (or send) a header that was larger doesn't make it legal. It is up to each client/server to determine whether it enforces the rules or not.

The recommended workaround is to "fold" the line. Refer to the spec on this.