diff --git a/ATTRIBUTION.md b/ATTRIBUTION.md
index e3c7f1c01e..f60a3a7c0f 100644
--- a/ATTRIBUTION.md
+++ b/ATTRIBUTION.md
@@ -28,3 +28,4 @@ FairEmail uses:
 * [Disconnect's tracker protection lists](https://github.com/disconnectme/disconnect-tracking-protection). Copyright 2010-2020 Disconnect, Inc. [Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International license](https://github.com/disconnectme/disconnect-tracking-protection/blob/master/LICENSE).
 * [Over-Scroll Support For Android's RecyclerView, ListView, GridView, ScrollView ...](https://github.com/EverythingMe/overscroll-decor). Copyright (c) 2015, DoAT Media Ltd. [BSD-2-Clause License](https://github.com/EverythingMe/overscroll-decor/blob/master/LICENSE)
 * [Compact Encoding Detection](https://github.com/google/compact_enc_det). Copyright 2016 Google Inc. [Apache License 2.0](https://github.com/google/compact_enc_det/blob/master/LICENSE).
+* [POI-HMEF](https://poi.apache.org/components/hmef/index.html). Copyright © 2001-2020 The Apache Software Foundation. [Apache Software License v2](https://poi.apache.org/devel/guidelines.html#The+Licensing).
diff --git a/app/build.gradle b/app/build.gradle
index 6565c895d2..de1bb20c7b 100644
--- a/app/build.gradle
+++ b/app/build.gradle
@@ -276,6 +276,7 @@ dependencies {
     def overscroll_version = "1.1.0"
     def appauth_version = "0.7.1"
     def jcharset_version = "2.1"
+    def apache_poi = "4.1.2"
 
     // https://developer.android.com/jetpack/androidx/releases/
 
@@ -436,4 +437,8 @@ dependencies {
     // http://www.freeutils.net/source/jcharset/
     // https://mvnrepository.com/artifact/net.freeutils/jcharset
     implementation "net.freeutils:jcharset:$jcharset_version"
+
+    // https://poi.apache.org/components/hmef/index.html
+    // https://mvnrepository.com/artifact/org.apache.poi/poi-scratchpad
+    implementation "org.apache.poi:poi-scratchpad:$apache_poi"
 }
diff --git a/app/src/main/assets/ATTRIBUTION.md b/app/src/main/assets/ATTRIBUTION.md
index e3c7f1c01e..f60a3a7c0f 100644
--- a/app/src/main/assets/ATTRIBUTION.md
+++ b/app/src/main/assets/ATTRIBUTION.md
@@ -28,3 +28,4 @@ FairEmail uses:
 * [Disconnect's tracker protection lists](https://github.com/disconnectme/disconnect-tracking-protection). Copyright 2010-2020 Disconnect, Inc. [Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International license](https://github.com/disconnectme/disconnect-tracking-protection/blob/master/LICENSE).
 * [Over-Scroll Support For Android's RecyclerView, ListView, GridView, ScrollView ...](https://github.com/EverythingMe/overscroll-decor). Copyright (c) 2015, DoAT Media Ltd. [BSD-2-Clause License](https://github.com/EverythingMe/overscroll-decor/blob/master/LICENSE)
 * [Compact Encoding Detection](https://github.com/google/compact_enc_det). Copyright 2016 Google Inc. [Apache License 2.0](https://github.com/google/compact_enc_det/blob/master/LICENSE).
+* [POI-HMEF](https://poi.apache.org/components/hmef/index.html). Copyright © 2001-2020 The Apache Software Foundation. [Apache Software License v2](https://poi.apache.org/devel/guidelines.html#The+Licensing).
diff --git a/app/src/main/java/eu/faircode/email/MessageHelper.java b/app/src/main/java/eu/faircode/email/MessageHelper.java
index 2b1d098715..6a632301e0 100644
--- a/app/src/main/java/eu/faircode/email/MessageHelper.java
+++ b/app/src/main/java/eu/faircode/email/MessageHelper.java
@@ -1940,6 +1940,10 @@ public class MessageHelper {
                 throw new IllegalArgumentException("Attachment not found");
 
             downloadAttachment(context, index, local);
+
+            if (Helper.isTnef(local.type) ||
+                    ("application/octet-stream".equals(local.type) && "winmail.dat".equals(local.name)))
+                decodeTNEF(context, local);
         }
 
         void downloadAttachment(Context context, int index, EntityAttachment local) throws MessagingException, IOException {
@@ -2058,6 +2062,87 @@ public class MessageHelper {
             }
         }
 
+        private void decodeTNEF(Context context, EntityAttachment local) {
+            try {
+                DB db = DB.getInstance(context);
+                int subsequence = 0;
+
+                // https://poi.apache.org/components/hmef/index.html
+                File file = local.getFile(context);
+                org.apache.poi.hmef.HMEFMessage msg = new org.apache.poi.hmef.HMEFMessage(new FileInputStream(file));
+
+                String subject = msg.getSubject();
+                if (!TextUtils.isEmpty(subject)) {
+                    EntityAttachment attachment = new EntityAttachment();
+                    attachment.message = local.message;
+                    attachment.sequence = local.sequence;
+                    attachment.subsequence = ++subsequence;
+                    attachment.name = "subject.txt";
+                    attachment.type = "text/plain";
+                    attachment.disposition = Part.ATTACHMENT;
+                    attachment.id = db.attachment().insertAttachment(attachment);
+
+                    Helper.writeText(attachment.getFile(context), subject);
+                    db.attachment().setDownloaded(attachment.id, (long) subject.length());
+                }
+
+                String body = msg.getBody();
+                if (!TextUtils.isEmpty(body)) {
+                    EntityAttachment attachment = new EntityAttachment();
+                    attachment.message = local.message;
+                    attachment.sequence = local.sequence;
+                    attachment.subsequence = ++subsequence;
+                    attachment.name = "document.rtf";
+                    attachment.type = "application/rtf";
+                    attachment.disposition = Part.ATTACHMENT;
+                    attachment.id = db.attachment().insertAttachment(attachment);
+
+                    Helper.writeText(attachment.getFile(context), body);
+                    db.attachment().setDownloaded(attachment.id, (long) body.length());
+                }
+
+                for (org.apache.poi.hmef.Attachment at : msg.getAttachments()) {
+                    EntityAttachment attachment = new EntityAttachment();
+                    attachment.message = local.message;
+                    attachment.sequence = local.sequence;
+                    attachment.subsequence = ++subsequence;
+                    attachment.name = at.getLongFilename();
+                    attachment.type = Helper.guessMimeType(attachment.name);
+                    attachment.disposition = Part.ATTACHMENT;
+                    attachment.id = db.attachment().insertAttachment(attachment);
+
+                    byte[] data = at.getContents();
+                    try (OutputStream os = new FileOutputStream(attachment.getFile(context))) {
+                        os.write(data);
+                    }
+
+                    db.attachment().setDownloaded(attachment.id, (long) data.length);
+                }
+
+                StringBuilder sb = new StringBuilder();
+                for (org.apache.poi.hmef.attribute.TNEFAttribute attr : msg.getMessageAttributes())
+                    sb.append(attr.toString()).append("\r\n");
+                for (org.apache.poi.hmef.attribute.MAPIAttribute attr : msg.getMessageMAPIAttributes())
+                    if (!org.apache.poi.hsmf.datatypes.MAPIProperty.RTF_COMPRESSED.equals(attr.getProperty()))
+                        sb.append(attr.toString()).append("\r\n");
+                if (sb.length() > 0) {
+                    EntityAttachment attachment = new EntityAttachment();
+                    attachment.message = local.message;
+                    attachment.sequence = local.sequence;
+                    attachment.subsequence = ++subsequence;
+                    attachment.name = "attributes.txt";
+                    attachment.type = "text/plain";
+                    attachment.disposition = Part.ATTACHMENT;
+                    attachment.id = db.attachment().insertAttachment(attachment);
+
+                    Helper.writeText(attachment.getFile(context), sb.toString());
+                    db.attachment().setDownloaded(attachment.id, (long) sb.length());
+                }
+            } catch (Throwable ex) {
+                Log.w(ex);
+            }
+        }
+
         String getWarnings(String existing) {
             if (existing != null)
                 warnings.add(0, existing);