MimeKit: NotSupportedException: No data is available for encoding 10000. For information on defining a custom encoding, see the documentation for the Encoding.RegisterProvider method.

public static void SendItemOptionAttachment(string from, string to, string subject, string bodyHtml, string attachment)
        {
            using var smtpSender = SmtpSender.Create(emailOptions.smtpHost)
               .SetCredential(emailOptions.login, emailOptions.password);

            var invalids = System.IO.Path.GetInvalidFileNameChars();
            subject = String.Join("_", subject.Split(invalids, StringSplitOptions.RemoveEmptyEntries)).TrimEnd('.');


            MimeEntity mimeEntity =  MimeEntity.Load(new ParserOptions() { CharsetEncoding = Encoding.UTF8 },new MemoryStream(Encoding.UTF8.GetPreamble().Concat(Encoding.UTF8.GetBytes(attachment ?? "")).ToArray()));
            
            from = emailOptions.fromName;
            try
            {
                smtpSender.WriteEmail
                                     .From(from)
                                     .To(to)
                                     .Subject(subject)
                                     .BodyHtml(bodyHtml)
                                     .Attach(mimeEntity)
                                     .Send();

            }
            catch (Exception ex)
            {
                Console.WriteLine(ex.Message);
            }


        }

This is one by ParserOptions method. MimeKit.dll!MimeKit.Utils.CharsetUtils.ProbeCharset(int codepage) crashes.

another one .Attach(new MemoryStream(Encoding.UTF8.GetPreamble().Concat(Encoding.UTF8.GetBytes(attachment ?? "")).ToArray()), $"{subject}_test.csv")

MimeKit.dll!MimeKit.Utils.CharsetUtils.ProbeCharset(int codepage)	crashes.

How it can be disabled? This CSV file contains BOM with UTF8 to support Excel correct encoding on CSV files with UTF8.