Make URL joining more robust

server/src/nm.rs

@@ -179,7 +179,7 @@ pub async fn thread(
             .get_first_value("date")
             .and_then(|d| mailparse::dateparse(&d).ok());
         let cid_prefix = shared::urls::cid_prefix(None, &id);
-        let base_url = Url::parse("https://there-should-be-no-relative-urls-in-email").unwrap();
+        let base_url = None;
         let body = match extract_body(&m, &id)? {
             Body::PlainText(PlainText { text, content_tree }) => {
                 let text = if text.len() > MAX_RAW_MESSAGE_SIZE {