improvements

src/mimeparser.rs

@@ -723,6 +723,8 @@ impl MimeMessage {
         !self.signatures.is_empty()
     }
 
+    /// Returns whether the email contains a `chat-version` header.
+    /// This indicates that email is a DC-email from a chat.
     pub(crate) fn has_chat_version(&self) -> bool {
         self.header.contains_key("chat-version")
     }