diff --git a/app/src/main/java/eu/faircode/email/EntityFolder.java b/app/src/main/java/eu/faircode/email/EntityFolder.java
index 108dd89db1..04c343f5ee 100644
--- a/app/src/main/java/eu/faircode/email/EntityFolder.java
+++ b/app/src/main/java/eu/faircode/email/EntityFolder.java
@@ -243,6 +243,7 @@ public class EntityFolder extends EntityOrder implements Serializable {
     }
 
     static String getType(String[] attrs, String fullName) {
+        // https://www.iana.org/assignments/imap-mailbox-name-attributes/imap-mailbox-name-attributes.xhtml
         for (String attr : attrs) {
             if ("\\Noselect".equals(attr) || "\\NonExistent".equals(attr))
                 return null;