diff --git a/src/main/java/io/kamax/mxisd/backend/memory/MemoryIdentityStore.java b/src/main/java/io/kamax/mxisd/backend/memory/MemoryIdentityStore.java
index dbebbd4..da53475 100644
--- a/src/main/java/io/kamax/mxisd/backend/memory/MemoryIdentityStore.java
+++ b/src/main/java/io/kamax/mxisd/backend/memory/MemoryIdentityStore.java
@@ -48,6 +48,7 @@ import java.util.List;
 import java.util.Optional;
 import java.util.function.Function;
 import java.util.function.Predicate;
+import java.util.stream.Collectors;
 
 public class MemoryIdentityStore implements AuthenticatorProvider, DirectoryProvider, IThreePidProvider, ProfileProvider {
 
@@ -171,4 +172,11 @@ public class MemoryIdentityStore implements AuthenticatorProvider, DirectoryProv
         }).orElseGet(BackendAuthResult::failure);
     }
 
+    @Override
+    public Iterable<ThreePidMapping> populateHashes() {
+        return cfg.getIdentities().stream()
+            .map(mic -> mic.getThreepids().stream().map(mtp -> new ThreePidMapping(mtp.getMedium(), mtp.getAddress(), mic.getUsername())))
+            .flatMap(s -> s).collect(
+            Collectors.toList());
+    }
 }
diff --git a/src/main/java/io/kamax/mxisd/backend/sql/SqlThreePidProvider.java b/src/main/java/io/kamax/mxisd/backend/sql/SqlThreePidProvider.java
index 2cabc3c..c70a042 100644
--- a/src/main/java/io/kamax/mxisd/backend/sql/SqlThreePidProvider.java
+++ b/src/main/java/io/kamax/mxisd/backend/sql/SqlThreePidProvider.java
@@ -36,6 +36,7 @@ import java.sql.PreparedStatement;
 import java.sql.ResultSet;
 import java.sql.SQLException;
 import java.util.ArrayList;
+import java.util.Collections;
 import java.util.List;
 import java.util.Optional;
 
@@ -104,4 +105,27 @@ public abstract class SqlThreePidProvider implements IThreePidProvider {
         return new ArrayList<>();
     }
 
+    @Override
+    public Iterable<ThreePidMapping> populateHashes() {
+        if (StringUtils.isBlank(cfg.getLookup().getQuery())) {
+            log.warn("Lookup query not configured, skip.");
+            return Collections.emptyList();
+        }
+
+        List<ThreePidMapping> result = new ArrayList<>();
+        try (Connection connection = pool.get()) {
+            PreparedStatement statement = connection.prepareStatement(cfg.getLookup().getQuery());
+            try (ResultSet resultSet = statement.executeQuery()) {
+                while (resultSet.next()) {
+                    String mxid = resultSet.getString("mxid");
+                    String medium = resultSet.getString("medium");
+                    String address = resultSet.getString("address");
+                    result.add(new ThreePidMapping(medium, address, mxid));
+                }
+            }
+        } catch (SQLException e) {
+            throw new RuntimeException(e);
+        }
+        return result;
+    }
 }
diff --git a/src/main/java/io/kamax/mxisd/config/sql/SqlConfig.java b/src/main/java/io/kamax/mxisd/config/sql/SqlConfig.java
index 6eb5ed3..44b2d57 100644
--- a/src/main/java/io/kamax/mxisd/config/sql/SqlConfig.java
+++ b/src/main/java/io/kamax/mxisd/config/sql/SqlConfig.java
@@ -124,6 +124,18 @@ public abstract class SqlConfig {
 
     }
 
+    public static class Lookup {
+        private String query;
+
+        public String getQuery() {
+            return query;
+        }
+
+        public void setQuery(String query) {
+            this.query = query;
+        }
+    }
+
     public static class Identity {
 
         private Boolean enabled;
@@ -264,6 +276,7 @@ public abstract class SqlConfig {
     private Directory directory = new Directory();
     private Identity identity = new Identity();
     private Profile profile = new Profile();
+    private Lookup lookup = new Lookup();
 
     public boolean isEnabled() {
         return enabled;
@@ -321,6 +334,14 @@ public abstract class SqlConfig {
         this.profile = profile;
     }
 
+    public Lookup getLookup() {
+        return lookup;
+    }
+
+    public void setLookup(Lookup lookup) {
+        this.lookup = lookup;
+    }
+
     protected abstract String getProviderName();
 
     public void build() {
@@ -354,6 +375,7 @@ public abstract class SqlConfig {
             log.info("Identity type: {}", getIdentity().getType());
             log.info("3PID mapping query: {}", getIdentity().getQuery());
             log.info("Identity medium queries: {}", GsonUtil.build().toJson(getIdentity().getMedium()));
+            log.info("Lookup query: {}", getLookup().getQuery());
             log.info("Profile:");
             log.info("  Enabled: {}", getProfile().isEnabled());
             if (getProfile().isEnabled()) {