SendAsync Method (String, String, String, String, Object)

SmtpClient.SendAsync Method (String, String, String, String, Object)

Sends an e-mail message to an SMTP server for delivery. The message sender, recipients, subject, and message body are specified using String objects. This method does not block the calling thread and allows the caller to pass an object to the method that is invoked when the operation completes.

Namespace: System.Net.Mail
Assembly: System (in system.dll)

public void SendAsync (
	string from,
	string recipients,
	string subject,
	string body,
	Object userToken
public void SendAsync (
	String from, 
	String recipients, 
	String subject, 
	String body, 
	Object userToken
public function SendAsync (
	from : String, 
	recipients : String, 
	subject : String, 
	body : String, 
	userToken : Object
Not applicable.



A String that contains the address information of the message sender.


A String that contains the address that the message is sent to.


A String that contains the subject line for the message.


A String that contains the message body.


A user-defined object that is passed to the method invoked when the asynchronous operation completes.

Exception typeCondition


from is a null reference (Nothing in Visual Basic).


recipient is a null reference (Nothing in Visual Basic).


from is Empty.


recipient is Empty.


This SmtpClient has a SendAsync call in progress.


Host is a null reference (Nothing in Visual Basic).


Host is equal to the empty string ("").


Port is zero.


This object has been disposed.


The connection to the SMTP server failed.


Authentication failed.


The operation timed out.


The message could not be delivered to one or more of the recipients in recipients.

To receive notification when the e-mail has been sent or the operation has been canceled, add an event handler to the SendCompleted event. You can cancel a SendAsync operation by calling the SendAsyncCancel method.

After calling SendAsync, you must wait for the e-mail transmission to complete before attempting to send another e-mail message using Send or SendAsync.

Before calling this method, the Host and Port properties must be set either through the configuration files or by setting the properties or passing this information into the SmtpClient(String,Int32) constructor.

If the SMTP host requires credentials, you must set them before calling this method. To specify credentials, use the UseDefaultCredentials or Credentials property.

If you receive an SmtpException exception, check the StatusCode property to find the reason the operation failed. The SmtpException can also contain an inner exception that indicates the reason the operation failed.

Your application can detect a server certificate validation error by examining the Error property passed into the SendCompletedEventHandler delegate.

The Timeout property does not have any effect on a SendAsync call.

To send mail and block while it is transmitted to the SMTP server, use one of the Send methods.

Windows 98, Windows Server 2000 SP4, Windows Millennium Edition, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The Microsoft .NET Framework 3.0 is supported on Windows Vista, Microsoft Windows XP SP2, and Windows Server 2003 SP1.

.NET Framework

Supported in: 3.0, 2.0

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