diff --git a/themis/search/indexer.py b/themis/search/indexer.py
index 4e24f3c..af45226 100644
--- a/themis/search/indexer.py
+++ b/themis/search/indexer.py
@@ -60,6 +60,26 @@ def mailCategoryTxtIndexer(obj):
 
 grok.global_adapter(mailCategoryTxtIndexer, name="mailCategoryTxt")
 
+@indexer(plone.dexterity.interfaces.IDexterityItem)
+def mailRelatedDocsTxtIndexer(obj):
+    if obj.portal_type not in ('courrier_entrant', 'courrier_sortant'):
+        return None
+    values = []
+    for attr in ('docs_related',):
+        if not hasattr(obj, attr):
+            continue
+        if getattr(obj, attr):
+            for relationvalue in getattr(obj, attr):
+                values.append(relationvalue.to_object.Title())
+    if values:
+        return ', '.join(values)
+    else:
+        return None
+
+grok.global_adapter(mailRelatedDocsTxtIndexer, name="mailRelatedDocsTxt")
+
+
+
 @indexer(plone.dexterity.interfaces.IDexterityItem)
 def docSessionIndexer(obj):
     if not '(D)' in obj.Type():
diff --git a/themis/search/profiles/default/catalog.xml b/themis/search/profiles/default/catalog.xml
index 8efc433..efba80e 100644
--- a/themis/search/profiles/default/catalog.xml
+++ b/themis/search/profiles/default/catalog.xml
@@ -66,6 +66,7 @@
   </index>
   <column value="mailContact"/>
   <column value="mailCategoryTxt"/>
+  <column value="mailRelatedDocsTxt"/>
   <column value="mailDate"/>
   <column value="docDate"/>
   <column value="docMeetingDate"/>