diff --git a/k9mail/src/main/java/com/fsck/k9/mailstore/MimePartStreamParser.java b/k9mail/src/main/java/com/fsck/k9/mailstore/MimePartStreamParser.java
index 3eb7d1962..574164f02 100644
--- a/k9mail/src/main/java/com/fsck/k9/mailstore/MimePartStreamParser.java
+++ b/k9mail/src/main/java/com/fsck/k9/mailstore/MimePartStreamParser.java
@@ -16,6 +16,7 @@ import com.fsck.k9.mail.Part;
 import com.fsck.k9.mail.internet.MimeBodyPart;
 import com.fsck.k9.mail.internet.MimeMessage;
 import com.fsck.k9.mail.internet.MimeMultipart;
+import com.fsck.k9.mail.internet.MimeUtility;
 import com.fsck.k9.mailstore.util.FileFactory;
 import org.apache.commons.io.IOUtils;
 import org.apache.james.mime4j.MimeException;
@@ -39,7 +40,7 @@ public class MimePartStreamParser {
                 .build();
 
         MimeStreamParser parser = new MimeStreamParser(parserConfig);
-        parser.setContentHandler(new PartBuilder(fileFactory, parsedRootPart));
+        parser.setContentHandler(new PartBuilder(parser, fileFactory, parsedRootPart));
         parser.setRecurse();
 
         try {
@@ -66,11 +67,17 @@ public class MimePartStreamParser {
 
 
     private static class PartBuilder implements ContentHandler {
+        private MimeStreamParser parser;
         private final FileFactory fileFactory;
         private final MimeBodyPart decryptedRootPart;
         private final Stack<Object> stack = new Stack<>();
 
-        public PartBuilder(FileFactory fileFactory, MimeBodyPart decryptedRootPart) {
+        private boolean isMessagePart;
+        private boolean isContentDispositionAttachment;
+
+        PartBuilder(MimeStreamParser parser, FileFactory fileFactory,
+                MimeBodyPart decryptedRootPart) {
+            this.parser = parser;
             this.fileFactory = fileFactory;
             this.decryptedRootPart = decryptedRootPart;
         }
@@ -111,11 +118,13 @@ public class MimePartStreamParser {
         @Override
         public void endBodyPart() throws MimeException {
             stack.pop();
+            parser.setRecurse();
         }
 
         @Override
         public void startHeader() throws MimeException {
-            // Do nothing
+            isMessagePart = false;
+            isContentDispositionAttachment = false;
         }
 
         @Override
@@ -125,11 +134,22 @@ public class MimePartStreamParser {
 
             Part part = (Part) stack.peek();
             part.addRawHeader(name, raw);
+
+            String fieldImmediateValue = MimeUtility.getHeaderParameter(parsedField.getBody(), null);
+            if ("Content-Type".equalsIgnoreCase(name) && MimeUtility.isMessage(fieldImmediateValue)) {
+                isMessagePart = true;
+            }
+
+            if ("Content-Disposition".equalsIgnoreCase(name) && "attachment".equalsIgnoreCase(fieldImmediateValue)) {
+                isContentDispositionAttachment = true;
+            }
         }
 
         @Override
         public void endHeader() throws MimeException {
-            // Do nothing
+            if (isMessagePart && isContentDispositionAttachment) {
+                parser.setFlat();
+            }
         }
 
         @Override
diff --git a/k9mail/src/test/java/com/fsck/k9/mailstore/MimePartStreamParserTest.kt b/k9mail/src/test/java/com/fsck/k9/mailstore/MimePartStreamParserTest.kt
new file mode 100644
index 000000000..f84467dbb
--- /dev/null
+++ b/k9mail/src/test/java/com/fsck/k9/mailstore/MimePartStreamParserTest.kt
@@ -0,0 +1,75 @@
+package com.fsck.k9.mailstore
+
+
+import java.io.ByteArrayInputStream
+
+import com.fsck.k9.mail.internet.MimeBodyPart
+import com.fsck.k9.mail.internet.MimeMessage
+import com.fsck.k9.mail.internet.MimeMultipart
+import org.junit.Test
+
+import org.junit.Assert.*
+
+
+class MimePartStreamParserTest {
+    @Test
+    fun innerMessage_DispositionInline() {
+        val msg = MimePartStreamParser.parse(null, ByteArrayInputStream(("""From: <x@example.org>
+To: <y@example.org>
+Subject: Testmail 1
+Content-Type: multipart/mixed; boundary=1
+
+--1
+Content-Type: text/plain
+
+some text in the first part
+--1
+Content-Type: message/rfc822; name="message"
+
+To: <z@example.org>
+Subject: Hi
+Date: now
+Content-Type: text/plain
+
+inner text
+--1--""").toByteArray()))
+
+        val body = msg.body as MimeMultipart
+        assertEquals(2, body.count.toLong())
+
+        val messagePart = body.getBodyPart(1) as MimeBodyPart
+        assertEquals("message/rfc822", messagePart.mimeType)
+        assertTrue(messagePart.body is MimeMessage)
+    }
+
+    @Test
+    fun innerMessage_dispositionAttachment() {
+        val msg = MimePartStreamParser.parse(null, ByteArrayInputStream(("""From: <x@example.org>
+To: <y@example.org>
+Subject: Testmail 2
+Content-Type: multipart/mixed; boundary=1
+
+--1
+Content-Type: text/plain
+
+some text in the first part
+--1
+Content-Type: message/rfc822; name="message"
+Content-Disposition: attachment
+
+To: <z@example.org>
+Subject: Hi
+Date: now
+Content-Type: text/plain
+
+inner text
+--1--""").toByteArray()))
+
+        val body = msg.body as MimeMultipart
+        assertEquals(2, body.count)
+
+        val messagePart = body.getBodyPart(1) as MimeBodyPart
+        assertEquals("message/rfc822", messagePart.mimeType)
+        assertTrue(messagePart.body is DeferredFileBody)
+    }
+}
\ No newline at end of file