Index: ../../../java/grails-plugins/grails-mail/test/unit/org/grails/mail/MailMessageBuilderTests.groovy
===================================================================
--- ../../../java/grails-plugins/grails-mail/test/unit/org/grails/mail/MailMessageBuilderTests.groovy	(revision 44701)
+++ ../../../java/grails-plugins/grails-mail/test/unit/org/grails/mail/MailMessageBuilderTests.groovy	Sun Aug 02 22:03:26 CEST 2009
@@ -21,6 +21,7 @@
 import org.codehaus.groovy.grails.commons.ConfigurationHolder
 import org.springframework.mail.MailSender
 import org.springframework.mail.javamail.JavaMailSender
+import javax.mail.internet.MimeMultipart
 
 /**
  * Test case for {@link MailMessageBuilder}.
@@ -127,6 +128,23 @@
         }
     }
 
+    void testAttachment() {
+        processDsl {
+            multipart true
+            to "fred@g2one.com"
+            subject "Hello Fred"
+            body 'How are you?'
+            attachBytes "dummy.bin", "application/binary", "abcdef".bytes
+        }
+        def msg = testBuilder.createMessage().mimeMessage
+        assertTrue msg.content instanceof MimeMultipart
+        assertEquals 2, msg.content.count
+
+        def attachment = msg.content.getBodyPart(1)
+        assertEquals "abcdef", attachment.content.text
+        assertEquals "dummy.bin", attachment.fileName
+    }
+
     private List to(MimeMessage msg) {
         msg.getRecipients(Message.RecipientType.TO)*.toString()
     }
Index: ../../../java/grails-plugins/grails-mail/src/groovy/org/grails/mail/MailMessageBuilder.groovy
===================================================================
--- ../../../java/grails-plugins/grails-mail/src/groovy/org/grails/mail/MailMessageBuilder.groovy	(revision 53895)
+++ ../../../java/grails-plugins/grails-mail/src/groovy/org/grails/mail/MailMessageBuilder.groovy	Sun Aug 02 22:06:58 CEST 2009
@@ -45,6 +45,7 @@
     
     MailSender mailSender
     MailService mailService
+    boolean multipart = false // by default, we're sending non-multipart emails
 
     MailMessageBuilder(MailService svc, MailSender mailSender) {
         this.mailSender = mailSender
@@ -54,7 +55,8 @@
     private MailMessage getMessage() {
         if(!message) {
             if(mailSender instanceof JavaMailSender) {
-                message = new MimeMailMessage(mailSender.createMimeMessage() )
+                def helper = new MimeMessageHelper(mailSender.createMimeMessage(), multipart)
+                message = new MimeMailMessage(helper)
             }
             else {
                 message = new SimpleMailMessage()
@@ -68,6 +70,11 @@
 
     MailMessage createMessage() { getMessage() }
 
+
+    void multipart(boolean multipart) {
+        this.multipart = multipart
+    }
+
     void to(String recip) {
         if(recip) {
             if (ConfigurationHolder.config.grails.mail.overrideAddress)
@@ -79,8 +86,8 @@
 	void attachBytes(String fileName, String contentType, byte[] bytes) {
 		def msg = getMessage()
 		if(msg instanceof MimeMailMessage) {
-			MimeMessageHelper message = new MimeMessageHelper(getMessage(), true, "UTF-8");
-		    message.addAttachment(fileName, new ByteArrayResource(bytes), contentType)			
+            assert multipart, "message is not marked as 'multipart'; use 'multipart true' as the first line in your builder DSL"
+            msg.mimeMessageHelper.addAttachment(fileName, new ByteArrayResource(bytes), contentType)
 		}
 		else {
 			throw new IllegalStateException("Message is not an instance of org.springframework.mail.javamail.MimeMessage, cannot attach bytes!")