<PackageReference Include="NETStandard.Library" Version="2.0.2" />

System.Net.Mail.SmtpFailedRecipientException

namespace System.Net.Mail { public class SmtpFailedRecipientException : SmtpException, ISerializable { public string FailedRecipient { get; } public SmtpFailedRecipientException(); public SmtpFailedRecipientException(SmtpStatusCode statusCode, string failedRecipient); public SmtpFailedRecipientException(SmtpStatusCode statusCode, string failedRecipient, string serverResponse); protected SmtpFailedRecipientException(SerializationInfo info, StreamingContext context); public SmtpFailedRecipientException(string message); public SmtpFailedRecipientException(string message, Exception innerException); public SmtpFailedRecipientException(string message, string failedRecipient, Exception innerException); } }