.NET GZipStream解压MIME中compressed-data报错，求解决方案

我需要解压MIME消息中标记为compressed-data的数据，编写了如下.NET代码：

using (var msi = new MemoryStream(content))
using (var mso = new MemoryStream())
{
    using (var gs = new GZipStream(msi, CompressionMode.Decompress))
    gs.CopyTo(mso);
    var a = mso.ToArray();
}

执行时抛出异常：

Found invalid data while encoding
at System.IO.Compression.InflaterZlib.Inflate(FlushCode flushCode)
at System.IO.Compression.InflaterZlib.ReadInflateOutput(Byte[] outputBuffer, Int32 offset, Int32 length, FlushCode flushCode, Int32& bytesRead)
at System.IO.Compression.InflaterZlib.Inflate(Byte[] bytes, Int32 offset, Int32 length)
at System.IO.Compression.DeflateStream.Read(Byte[] array, Int32 offset, Int32 count)
at System.IO.Compression.GZipStream.Read(Byte[] array, Int32 offset, Int32 count)
at System.IO.Stream.InternalCopyTo(Stream destination, Int32 bufferSize)
at System.IO.Stream.CopyTo(Stream destination)

根据RFC规范，该数据应为标准GZIP格式。查看MimeKit代码后发现，其底层使用BouncyCastle的CmsCompressedDataParser可成功解压相同数据：

var cdata = File.ReadAllBytes("C://test//as2//CompressedContentPartContent.bin");
CmsCompressedDataParser ed = new CmsCompressedDataParser(cdata);
var aa = CmsTestUtil.StreamToByteArray(ed.GetContent().ContentStream);

但公司政策要求避免使用第三方库，因此困惑为何.NET标准库的GZipStream和DeflateStream均报错，而CmsCompressedDataParser可正常工作？另外尝试SharpZipLib也失败，错误信息如下：

Error GZIP header, first magic byte doesn't match
at ICSharpCode.SharpZipLib.GZip.GZipInputStream.ReadHeader()
at ICSharpCode.SharpZipLib.GZip.GZipInputStream.Read(Byte[] buffer, Int32 offset, Int32 count)
at ICSharpCode.SharpZipLib.Core.StreamUtils.Copy(Stream source, Stream destination, Byte[] buffer)
at ICSharpCode.SharpZipLib.GZip.GZip.Decompress(Stream inStream, Stream outStream, Boolean isStreamOwner)

我对比了两份数据的头部字节，结果匹配，求问问题原因。

内容的提问来源于stack exchange，提问作者katit