Umlauts in encrypted headings 
When I sent a mail with the heading "Test verschlüsselt", it after receiving it read "?ISO-8859-1?Q?Test_verschl=FCsselt_?=". 
diff --git a/app/core/src/main/java/com/fsck/k9/mailstore/MessageViewInfoExtractor.java b/app/core/src/main/java/com/fsck/k9/mailstore/MessageViewInfoExtractor.java
index 3d902654e..4499e955b 100644
--- a/app/core/src/main/java/com/fsck/k9/mailstore/MessageViewInfoExtractor.java
+++ b/app/core/src/main/java/com/fsck/k9/mailstore/MessageViewInfoExtractor.java
@@ -107,7 +107,7 @@ public class MessageViewInfoExtractor {
 
         boolean hasProtectedSubject = "v1".equalsIgnoreCase(protectedHeadersParam) && protectedSubjectHeader.length > 0;
         if (hasProtectedSubject) {
-            return protectedSubjectHeader[0];
+            return MimeUtility.unfoldAndDecode(protectedSubjectHeader[0]);
         }
 
         return null;
['app/core/src/main/java/com/fsck/k9/mailstore/MessageViewInfoExtractor.java']