Utility Features - SMTP Client

Listing Extension Servers using Smtp Client

Aspose.Email SmtpClient lets you retrieve the server extensions that a server supports such as IDLE, UNSELECT, QUOTA, etc. This helps in identifying the availability of an extension before using the client for that particular functionality. The getCapabilities() method returns the supported extension types in the form of a string array.

Retrieving Server Extensions

The following code snippet shows you how to retrieve server extensions.

// For complete examples and data files, please go to https://github.com/aspose-email/Aspose.Email-for-Java

SmtpClient client = new SmtpClient("smtp.gmail.com",587,"username","password");
client.setSecurityOptions(SecurityOptions.Auto);
String[] caps = client.getCapabilities();
for (String str:caps)
	System.out.println(str);

Working with Signed Message

Aspose.Email API provides the capability to create Signed messages using certificates. The attachSignature method of the MailMessage class can be used to sign a message for saving or even sending it using the SmtpClient.

Please note that the Aspose.Email for Java API depends on Bouncy Castle for cryptography features.

Bouncy Castle Maven Dependencies

<dependency>
<groupId>org.bouncycastle</groupId>
<artifactId>bcprov-jdk15on</artifactId>
<version>1.60</version>
</dependency>

<dependency>
<groupId>org.bouncycastle</groupId>
<artifactId>bcpkix-jdk15on</artifactId>
<version>1.60</version>
</dependency>

Enable Bouncy Castle Security Provider

import java.security.Security;
import org.bouncycastle.jce.provider.BouncyCastleProvider;

if (Security.getProvider("BC") == null)
    Security.addProvider(new BouncyCastleProvider());

Sign a Message

The following code snippet shows you how to Sign a Message.

// For complete examples and data files, please go to https://github.com/aspose-email/Aspose.Email-for-Java

byte[] privateCert = Files.readAllBytes(new File("sample.pfx").toPath());
byte[] publicCert = Files.readAllBytes(new File("sample.cer").toPath());

MailMessage msg = new MailMessage("[e-mail]", "[e-mail]", "Signed message only", "Test Body of signed message");
MailMessage signed = msg.attachSignature(privateCert, "password");
MailMessage encrypted = signed.encrypt(publicCert, "password");
MailMessage decrypted = encrypted.decrypt(privateCert, "password");
MailMessage unsigned = decrypted.removeSignature();// The original message with proper body
MapiMessage mapi = MapiMessage.fromMailMessage(unsigned);

Using Detached Certificate Option

Web-based email clients may not be able to display body contents of a Signed message. This can be taken care of by detaching the certificate before sending it to web-based email clients. The detached flag in the overloaded method of attachSignature can be used to achieve this. If set to true, the certificate is detached from the email and vice versa. To see Signed Message body in Web-based clients, you need to create MailMessage with detached signature. The following code snippet shows you how to use detached certificate option.

// For complete examples and data files, please go to https://github.com/aspose-email/Aspose.Email-for-Java

MailMessage msg = new MailMessage("[e-mail]", "[e-mail]", "subject:Signed message only by AE", "body:Test Body of signed message by AE");
MailMessage signed = msg.attachSignature(privateCert, "password", true);
SmtpClient smtp = getSmtpClient(); //some test smtp client

smtp.send(signed);