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SmtpClientConnectAsync Method (Stream, String, Int32, SecureSocketOptions, CancellationToken)

Asynchronously establish a connection to the specified SMTP or SMTP/S server using the provided socket.

Namespace:  MailKit.Net.Smtp
Assembly:  MailKit (in MailKit.dll) Version: 3.0.0
public override Task ConnectAsync(
	Stream stream,
	string host,
	int port = 0,
	SecureSocketOptions options = SecureSocketOptions.Auto,
	CancellationToken cancellationToken = default


Type: System.IOStream
The stream to use for the connection.
Type: SystemString
The host name to connect to.
port (Optional)
Type: SystemInt32
The port to connect to. If the specified port is 0, then the default port will be used.
options (Optional)
Type: MailKit.SecuritySecureSocketOptions
The secure socket options to when connecting.
cancellationToken (Optional)
Type: System.ThreadingCancellationToken
The cancellation token.

Return Value

Type: Task
An asynchronous task context.


IMailServiceConnectAsync(Stream, String, Int32, SecureSocketOptions, CancellationToken)
IMailServiceConnectAsync(Stream, String, Int32, SecureSocketOptions, CancellationToken)

stream is null.


host is null.

ArgumentOutOfRangeExceptionport is not between 0 and 65535.
ArgumentException The host is a zero-length string.
ObjectDisposedException The SmtpClient has been disposed.
InvalidOperationException The SmtpClient is already connected.
NotSupportedExceptionoptions was set to StartTls and the SMTP server does not support the STARTTLS extension.
OperationCanceledException The operation was canceled.
SslHandshakeException An error occurred during the SSL/TLS negotiations.
IOException An I/O error occurred.
SmtpCommandException An SMTP command failed.
SmtpProtocolException An SMTP protocol error occurred.

Establishes a connection to the specified SMTP or SMTP/S server using the provided socket.

If the options has a value of Auto, then the port is used to determine the default security options. If the port has a value of 465, then the default options used will be SslOnConnect. All other values will use StartTlsWhenAvailable.

Once a connection is established, properties such as AuthenticationMechanisms and Capabilities will be populated.

Note Note
With the exception of using the port to determine the default SecureSocketOptions to use when the options value is Auto, the host and port parameters are only used for logging purposes.
See Also