diff --git a/app/src/main/java/eu/faircode/email/MessageHelper.java b/app/src/main/java/eu/faircode/email/MessageHelper.java
index 73b2f36bd2..5f51ee9723 100644
--- a/app/src/main/java/eu/faircode/email/MessageHelper.java
+++ b/app/src/main/java/eu/faircode/email/MessageHelper.java
@@ -535,6 +535,7 @@ public class MessageHelper {
         private Part plain = null;
         private Part html = null;
         private List<AttachmentPart> attachments = new ArrayList<>();
+        private List<String> warnings = new ArrayList<>();
 
         String getHtml() throws MessagingException {
             if (plain == null && html == null)
@@ -559,6 +560,16 @@ public class MessageHelper {
                 result = ex + "\n" + android.util.Log.getStackTraceString(ex);
             }
 
+            ContentType ct = new ContentType(part.getContentType());
+            String charset = ct.getParameter("charset");
+            if (TextUtils.isEmpty(charset))
+                warnings.add("Missing charset");
+            else {
+                if ("US-ASCII".equals(Charset.forName(charset).name()) &&
+                        !"US-ASCII".equals(charset.toUpperCase()))
+                    warnings.add("Unknown charset " + charset);
+            }
+
             if (part.isMimeType("text/plain") || text)
                 result = "<pre>" + result.replaceAll("\\r?\\n", "<br />") + "</pre>";
 
@@ -666,6 +677,13 @@ public class MessageHelper {
                     os.close();
             }
         }
+
+        String getWarnings() {
+            if (warnings.size() == 0)
+                return null;
+            else
+                return TextUtils.join(", ", warnings);
+        }
     }
 
     private class AttachmentPart {
diff --git a/app/src/main/java/eu/faircode/email/ServiceSynchronize.java b/app/src/main/java/eu/faircode/email/ServiceSynchronize.java
index 31baa75f3d..4cfec61ad6 100644
--- a/app/src/main/java/eu/faircode/email/ServiceSynchronize.java
+++ b/app/src/main/java/eu/faircode/email/ServiceSynchronize.java
@@ -2628,6 +2628,9 @@ public class ServiceSynchronize extends LifecycleService {
                     String body = parts.getHtml();
                     message.write(context, body);
                     db.message().setMessageContent(message.id, true, HtmlHelper.getPreview(body));
+                    String warnings = parts.getWarnings();
+                    if (warnings != null)
+                        db.message().setMessageError(message.id, warnings);
                     Log.i(folder.name + " downloaded message id=" + message.id + " size=" + message.size);
                 }