diff --git a/src/com/fsck/k9/mail/transport/SmtpDataStuffing.java b/src/com/fsck/k9/mail/transport/SmtpDataStuffing.java
new file mode 100644
index 000000000..110042028
--- /dev/null
+++ b/src/com/fsck/k9/mail/transport/SmtpDataStuffing.java
@@ -0,0 +1,43 @@
+package com.fsck.k9.mail.transport;
+
+import java.io.FilterOutputStream;
+import java.io.IOException;
+import java.io.OutputStream;
+
+public class SmtpDataStuffing extends FilterOutputStream
+{
+    private static final int STATE_NORMAL = 0;
+    private static final int STATE_CR = 1;
+    private static final int STATE_CRLF = 2;
+    
+    private int state = STATE_NORMAL;
+
+    public SmtpDataStuffing(OutputStream out)
+    {
+        super(out);
+    }
+
+    @Override
+    public void write(int oneByte) throws IOException
+    {
+        if (oneByte == '\r')
+        {
+            state = STATE_CR;
+        }
+        else if ((state == STATE_CR) && (oneByte == '\n'))
+        {
+            state = STATE_CRLF;
+        }
+        else if ((state == STATE_CRLF) && (oneByte == '.'))
+        {
+            // Read <CR><LF><DOT> so this line needs an additional period.
+            super.write('.');
+            state = STATE_NORMAL;
+        }
+        else
+        {
+            state = STATE_NORMAL;
+        }
+        super.write(oneByte);
+    }
+}
diff --git a/src/com/fsck/k9/mail/transport/SmtpTransport.java b/src/com/fsck/k9/mail/transport/SmtpTransport.java
index c433d2f21..a7b15f7d7 100644
--- a/src/com/fsck/k9/mail/transport/SmtpTransport.java
+++ b/src/com/fsck/k9/mail/transport/SmtpTransport.java
@@ -317,9 +317,9 @@ public class SmtpTransport extends Transport
             message.setRecipients(RecipientType.BCC, null);
             executeSimpleCommand("DATA");
             
-            //TODO: Data stuffing (RFC 821 4.5.2.)
             EOLConvertingOutputStream msgOut = new EOLConvertingOutputStream(
-                    new BufferedOutputStream(mOut, 1024)); 
+                    new SmtpDataStuffing(
+                            new BufferedOutputStream(mOut, 1024)));
 
             message.writeTo(msgOut);