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+====== MailService in OSGi ======
+OSGi itself doesn't provide you with a mail service and most osgi container don't provide one either. But it is not very difficult to write a simple mail service yourself.
+===== Step 1: Install Apache Commons Email =====
+Apache Commons Email does the heavy lifting when it comes to sending emails.
+  install mvn:org.apache.commons/commons-email/1.3.3
+===== Step 2: MailService =====
+This sample service is all you need for a start:
+<sxh java>
+public class MailService {
+    public void send(String subject, String message, String receiver) {
+        // backup classloader
+        ClassLoader cl = Thread.currentThread().getContextClassLoader();
+        try {
+            //  switch to tccl so that javamail can resolve data content handlers
+            Thread.currentThread().setContextClassLoader(javax.mail.Session.class.getClassLoader());
+            Email email = new SimpleEmail();
+            email.setHostName(mailHost);
+            email.setSmtpPort(mailPort);
+            email.setFrom(mailSender);
+            email.addTo(receiver);
+            email.setSubject(subject);
+            email.setMsg(message);
+            email.send();
+        }
+        catch(Exception e) {
+            logger.error("E-mail konnte nicht versandt werden.", e);
+        }
+        finally {
+            // set original classloader
+            Thread.currentThread().setContextClassLoader(cl);
+        }
+    }
+}
+</sxh>
+<note important>You need to take of classloaders as the javax.mail package from Sun/Oracle does some assumptions on classloaders which are not met in an OSGi environment.</note>
+===== Step 3 : Configuration =====
+You probably want to keep the service configurable. So you best use the ConfigAdmin for configuration and implement the ManagedService interface.
+<sxh java>
+public class MailService implements IMailService, ManagedService {
+    ...
+    @Override
+    public void updated(Dictionary<String, ?> properties) throws ConfigurationException {
+        if (properties == null || properties.isEmpty()) {
+            return;
+        }
+        Object value = properties.get("mail.host");
+        if (value != null) {
+            mailHost = value.toString();
+        }
+        value = properties.get("mail.port");
+        if (value != null) {
+            mailPort = Integer.parseInt(value.toString());
+        }
+        value = properties.get("mail.sender");
+        if (value != null) {
+            mailSender = value.toString();
+        }
+    }
+}
+</sxh>
+{{tag>java osgi}}