HA-JavaMail: High-Availability JavaMail

HA-JavaMail is a JavaMail transport proxy that adds efficiency and reliability to an underlying JavaMail provider.

HA-JavaMail is NOT an SMTP implementation - it's a wrapper around an existing implementation that provides several client-side optimizations designed to maximize throughput.

	Features

• High-Availibility
• Manages connections to multiple mail servers.
• Message sending will retry with the next available transport until successful.
• Detected dead connections are automatically re-opened and made available.
• Efficiency
• Messages are sent asynchronously to minimize impact of network latency between client and mail server.
• Configurable sending strategies, e.g. email address host grouping minimizes work required to lookup domains.
• Tranparent integration
• Implements the javax.mail.Transport interface
• Integration is as simple as placing HA-JavaMail jar file into classpath.

	Sample Usage

e.g.

java.util.Properties properties = new java.util.Properties();
properties.setProperty("mail.transport.protocol", "smtp");
properties.setProperty("mail.host", "mail1.domain.com,mail2.domain.com");
properties.setProperty("mail.transport.pool-size", "10");

javax.mail.Session session = javax.mail.Session.getInstance(properties);
javax.mail.Transport transport = session.getTransport();

long startTime = System.currentTimeMillis();

transport.connect();

javax.mail.Address address = new javax.mail.internet.InternetAddress("test@domain.com");

for (int i = 1; i ≤ 100; ++i)
{
    javax.mail.Message message = new javax.mail.internet.MimeMessage(session);
    message.setRecipient(javax.mail.Message.RecipientType.TO, address);
    message.setSubject("Test #" + i);
    message.setText("");

    transport.sendMessage(message, message.getAllRecipients());
}

transport.close();

long endTime = System.currentTimeMillis();
System.out.println("Total execution time = " + (startTime - endTime) + " ms");

HA-JavaMail is configured entirely via session properties.

Session Property	Default	Description
mail.host or mail.protocol.host	Required	Comma seperated list of mail server host names.
mail.transport.pool-size	1	Number of connections to manage per server.
mail.transport.connect-timeout	0	Number of seconds to wait for the first successful transport connection before timing out. 0 means wait forever.
mail.transport.connect-retry-period	60	Number of seconds to wait between transport connection attempts.
mail.transport.sender-strategy	net.sf.hajavamail.SimpleSenderStrategy	net.sf.hajavamail.SenderStrategy implementation used to send mail. Also available out of the box is net.sf.hajavamail.HostGroupingSenderStrategy.

Using HA-JavaMail in conjunction with Sun's JavaMail implementation is significantly faster than Sun's JavaMail implementation alone.

Note: HA-JavaMail (number of servers * Pool size)