diff --git a/src/dc_mimeparser.rs b/src/dc_mimeparser.rs
index 9b00e4cc9..fdc991a59 100644
--- a/src/dc_mimeparser.rs
+++ b/src/dc_mimeparser.rs
@@ -1453,10 +1453,9 @@ pub unsafe fn mailmime_transfer_decode(
     1
 }
 
-// TODO should return bool /rtn
-pub unsafe fn dc_mimeparser_is_mailinglist_message(mimeparser: &dc_mimeparser_t) -> libc::c_int {
+pub unsafe fn dc_mimeparser_is_mailinglist_message(mimeparser: &dc_mimeparser_t) -> bool {
     if !dc_mimeparser_lookup_field(&mimeparser, "List-Id").is_null() {
-        return 1i32;
+        return true;
     }
     let precedence: *mut mailimf_optional_field =
         dc_mimeparser_lookup_optional_field(mimeparser, "Precedence");
@@ -1470,11 +1469,11 @@ pub unsafe fn dc_mimeparser_is_mailinglist_message(mimeparser: &dc_mimeparser_t)
                 b"bulk\x00" as *const u8 as *const libc::c_char,
             ) == 0i32
         {
-            return 1i32;
+            return true;
         }
     }
 
-    0
+    false
 }
 
 pub unsafe fn dc_mimeparser_sender_equals_recipient(mimeparser: &dc_mimeparser_t) -> libc::c_int {
diff --git a/src/dc_receive_imf.rs b/src/dc_receive_imf.rs
index 85c30566d..75aec7ec0 100644
--- a/src/dc_receive_imf.rs
+++ b/src/dc_receive_imf.rs
@@ -445,7 +445,7 @@ unsafe fn add_parts(
 
         if *chat_id == 0 {
             // check if the message belongs to a mailing list
-            if 0 != dc_mimeparser_is_mailinglist_message(mime_parser) {
+            if dc_mimeparser_is_mailinglist_message(mime_parser) {
                 *chat_id = 3;
                 info!(
                     context,
@@ -1258,7 +1258,7 @@ unsafe fn create_or_lookup_group(
         .get_config(context, "configured_addr")
         .unwrap_or_default();
     if chat_id == 0
-            && 0 == dc_mimeparser_is_mailinglist_message(mime_parser)
+            && !dc_mimeparser_is_mailinglist_message(mime_parser)
             && !grpid.is_empty()
             && !grpname.is_null()
             // otherwise, a pending "quit" message may pop up
@@ -1493,7 +1493,7 @@ unsafe fn create_or_lookup_adhoc_group(
     };
 
     // build member list from the given ids
-    if to_ids.is_empty() || 0 != dc_mimeparser_is_mailinglist_message(mime_parser) {
+    if to_ids.is_empty() || dc_mimeparser_is_mailinglist_message(mime_parser) {
         // too few contacts or a mailinglist
         cleanup(
             grpname,