Fixed deleting message/rfc822 attachments

app/src/main/java/eu/faircode/email/Core.java

@@ -126,6 +126,7 @@ import javax.mail.Store;
 import javax.mail.StoreClosedException;
 import javax.mail.UIDFolder;
 import javax.mail.internet.AddressException;
+import javax.mail.internet.ContentType;
 import javax.mail.internet.InternetAddress;
 import javax.mail.internet.MimeBodyPart;
 import javax.mail.internet.MimeMessage;
@@ -2170,6 +2171,15 @@ class Core {
 
                     multipart.removeBodyPart(i);
 
+                    try {
+                        // Can't upload empty message/rfc822
+                        ContentType ct = new ContentType(contentType);
+                        if ("message/rfc822".equalsIgnoreCase(ct.getBaseType()))
+                            contentType = "application/octet-stream";
+                    } catch (Throwable ex) {
+                        Log.w(ex);
+                    }
+
                     BodyPart placeholderPart = new MimeBodyPart();
                     placeholderPart.setContent("", contentType);
                     placeholderPart.setFileName(fileName);