diff --git a/e2e-tests/src/test/resources/data/com/google/gerrit/scenarios/CheckProjectsCacheFlushEntries.json b/e2e-tests/src/test/resources/data/com/google/gerrit/scenarios/CheckProjectsCacheFlushEntries.json
new file mode 100644
index 0000000..6210deb
--- /dev/null
+++ b/e2e-tests/src/test/resources/data/com/google/gerrit/scenarios/CheckProjectsCacheFlushEntries.json
@@ -0,0 +1,6 @@
+[
+  {
+    "url": "http://HOSTNAME:HTTP_PORT/a/config/server/caches/projects",
+    "entries": "PROJECTS_ENTRIES"
+  }
+]
diff --git a/e2e-tests/src/test/resources/data/com/google/gerrit/scenarios/FlushProjectsCache.json b/e2e-tests/src/test/resources/data/com/google/gerrit/scenarios/FlushProjectsCache.json
new file mode 100644
index 0000000..9ff15a7
--- /dev/null
+++ b/e2e-tests/src/test/resources/data/com/google/gerrit/scenarios/FlushProjectsCache.json
@@ -0,0 +1,5 @@
+[
+  {
+    "url": "http://HOSTNAME:HTTP_PORT/a/config/server/caches/projects/flush"
+  }
+]
diff --git a/e2e-tests/src/test/resources/data/com/google/gerrit/scenarios/GetProjectsCacheEntries.json b/e2e-tests/src/test/resources/data/com/google/gerrit/scenarios/GetProjectsCacheEntries.json
new file mode 100644
index 0000000..fcf4bc9
--- /dev/null
+++ b/e2e-tests/src/test/resources/data/com/google/gerrit/scenarios/GetProjectsCacheEntries.json
@@ -0,0 +1,5 @@
+[
+  {
+    "url": "http://HOSTNAME:HTTP_PORT/a/config/server/caches/projects"
+  }
+]
diff --git a/e2e-tests/src/test/scala/com/google/gerrit/scenarios/CacheFlushSimulation.scala b/e2e-tests/src/test/scala/com/google/gerrit/scenarios/CacheFlushSimulation.scala
new file mode 100644
index 0000000..98d0190
--- /dev/null
+++ b/e2e-tests/src/test/scala/com/google/gerrit/scenarios/CacheFlushSimulation.scala
@@ -0,0 +1,32 @@
+// Copyright (C) 2020 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.gerrit.scenarios
+
+class CacheFlushSimulation extends GerritSimulation {
+  protected val entriesKey = "entries"
+  protected val memKey = "mem"
+  protected var producer: Option[CacheFlushSimulation] = None
+  protected var consumer: Option[CacheFlushSimulation] = None
+
+  private var cacheEntriesBeforeFlush: Int = 0
+
+  def entriesBeforeFlush(entries: Int): Unit = {
+    cacheEntriesBeforeFlush = entries
+  }
+
+  def expectedEntriesAfterFlush(): Int = {
+    cacheEntriesBeforeFlush - 1
+  }
+}
diff --git a/e2e-tests/src/test/scala/com/google/gerrit/scenarios/CheckProjectsCacheFlushEntries.scala b/e2e-tests/src/test/scala/com/google/gerrit/scenarios/CheckProjectsCacheFlushEntries.scala
new file mode 100644
index 0000000..040e5cf
--- /dev/null
+++ b/e2e-tests/src/test/scala/com/google/gerrit/scenarios/CheckProjectsCacheFlushEntries.scala
@@ -0,0 +1,48 @@
+// Copyright (C) 2020 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.gerrit.scenarios
+
+import io.gatling.core.Predef.{atOnceUsers, _}
+import io.gatling.core.feeder.FeederBuilder
+import io.gatling.core.structure.ScenarioBuilder
+import io.gatling.http.Predef._
+
+class CheckProjectsCacheFlushEntries extends CacheFlushSimulation {
+  private val data: FeederBuilder = jsonFile(resource).convert(keys).queue
+
+  def this(producer: CacheFlushSimulation) {
+    this()
+    this.producer = Some(producer)
+  }
+
+  val test: ScenarioBuilder = scenario(unique)
+      .feed(data)
+      .exec(session => {
+        if (producer.nonEmpty) {
+          session.set(entriesKey, producer.get.expectedEntriesAfterFlush())
+        } else {
+          session
+        }
+      })
+      .exec(http(unique).get("${url}")
+          .check(regex("\"" + memKey + "\": (\\d+)")
+              .is(session => session(entriesKey).as[String])))
+
+  setUp(
+    test.inject(
+      atOnceUsers(1)
+    ),
+  ).protocols(httpProtocol)
+}
diff --git a/e2e-tests/src/test/scala/com/google/gerrit/scenarios/CloneUsingBothProtocols.scala b/e2e-tests/src/test/scala/com/google/gerrit/scenarios/CloneUsingBothProtocols.scala
index ab91185..c70c393 100644
--- a/e2e-tests/src/test/scala/com/google/gerrit/scenarios/CloneUsingBothProtocols.scala
+++ b/e2e-tests/src/test/scala/com/google/gerrit/scenarios/CloneUsingBothProtocols.scala
@@ -15,13 +15,13 @@
 package com.google.gerrit.scenarios
 
 import io.gatling.core.Predef._
-import io.gatling.core.feeder.FileBasedFeederBuilder
+import io.gatling.core.feeder.FeederBuilder
 import io.gatling.core.structure.ScenarioBuilder
 
 import scala.concurrent.duration._
 
 class CloneUsingBothProtocols extends GitSimulation {
-  private val data: FileBasedFeederBuilder[Any]#F#F = jsonFile(resource).convert(keys).queue
+  private val data: FeederBuilder = jsonFile(resource).convert(keys).queue
   private val default: String = name
   private val duration: Int = 2
 
diff --git a/e2e-tests/src/test/scala/com/google/gerrit/scenarios/CreateChange.scala b/e2e-tests/src/test/scala/com/google/gerrit/scenarios/CreateChange.scala
index 39b6d42..a5d7358 100644
--- a/e2e-tests/src/test/scala/com/google/gerrit/scenarios/CreateChange.scala
+++ b/e2e-tests/src/test/scala/com/google/gerrit/scenarios/CreateChange.scala
@@ -15,14 +15,14 @@
 package com.google.gerrit.scenarios
 
 import io.gatling.core.Predef.{atOnceUsers, _}
-import io.gatling.core.feeder.FileBasedFeederBuilder
+import io.gatling.core.feeder.FeederBuilder
 import io.gatling.core.structure.ScenarioBuilder
 import io.gatling.http.Predef._
 
 import scala.concurrent.duration._
 
 class CreateChange extends GerritSimulation {
-  private val data: FileBasedFeederBuilder[Any]#F#F = jsonFile(resource).convert(keys).queue
+  private val data: FeederBuilder = jsonFile(resource).convert(keys).queue
   private val default: String = name
   private val numberKey = "_number"
 
diff --git a/e2e-tests/src/test/scala/com/google/gerrit/scenarios/CreateProject.scala b/e2e-tests/src/test/scala/com/google/gerrit/scenarios/CreateProject.scala
index 12340a5..3d5e677 100644
--- a/e2e-tests/src/test/scala/com/google/gerrit/scenarios/CreateProject.scala
+++ b/e2e-tests/src/test/scala/com/google/gerrit/scenarios/CreateProject.scala
@@ -15,11 +15,11 @@
 package com.google.gerrit.scenarios
 
 import io.gatling.core.Predef._
-import io.gatling.core.feeder.FileBasedFeederBuilder
+import io.gatling.core.feeder.FeederBuilder
 import io.gatling.core.structure.ScenarioBuilder
 
 class CreateProject extends ProjectSimulation {
-  private val data: FileBasedFeederBuilder[Any]#F#F = jsonFile(resource).convert(keys).queue
+  private val data: FeederBuilder = jsonFile(resource).convert(keys).queue
 
   def this(default: String) {
     this()
diff --git a/e2e-tests/src/test/scala/com/google/gerrit/scenarios/DeleteChange.scala b/e2e-tests/src/test/scala/com/google/gerrit/scenarios/DeleteChange.scala
index f3a2d14..a5d3801 100644
--- a/e2e-tests/src/test/scala/com/google/gerrit/scenarios/DeleteChange.scala
+++ b/e2e-tests/src/test/scala/com/google/gerrit/scenarios/DeleteChange.scala
@@ -15,12 +15,12 @@
 package com.google.gerrit.scenarios
 
 import io.gatling.core.Predef.{atOnceUsers, _}
-import io.gatling.core.feeder.FileBasedFeederBuilder
+import io.gatling.core.feeder.FeederBuilder
 import io.gatling.core.structure.ScenarioBuilder
 import io.gatling.http.Predef.http
 
 class DeleteChange extends GerritSimulation {
-  private val data: FileBasedFeederBuilder[Any]#F#F = jsonFile(resource).convert(keys).queue
+  private val data: FeederBuilder = jsonFile(resource).convert(keys).queue
   var number: Option[Int] = None
 
   override def relativeRuntimeWeight = 2
diff --git a/e2e-tests/src/test/scala/com/google/gerrit/scenarios/DeleteProject.scala b/e2e-tests/src/test/scala/com/google/gerrit/scenarios/DeleteProject.scala
index 4b01fd7..983ac0b 100644
--- a/e2e-tests/src/test/scala/com/google/gerrit/scenarios/DeleteProject.scala
+++ b/e2e-tests/src/test/scala/com/google/gerrit/scenarios/DeleteProject.scala
@@ -15,11 +15,11 @@
 package com.google.gerrit.scenarios
 
 import io.gatling.core.Predef._
-import io.gatling.core.feeder.FileBasedFeederBuilder
+import io.gatling.core.feeder.FeederBuilder
 import io.gatling.core.structure.ScenarioBuilder
 
 class DeleteProject extends ProjectSimulation {
-  private val data: FileBasedFeederBuilder[Any]#F#F = jsonFile(resource).convert(keys).queue
+  private val data: FeederBuilder = jsonFile(resource).convert(keys).queue
 
   def this(default: String) {
     this()
diff --git a/e2e-tests/src/test/scala/com/google/gerrit/scenarios/FlushProjectsCache.scala b/e2e-tests/src/test/scala/com/google/gerrit/scenarios/FlushProjectsCache.scala
new file mode 100644
index 0000000..94f4ae3
--- /dev/null
+++ b/e2e-tests/src/test/scala/com/google/gerrit/scenarios/FlushProjectsCache.scala
@@ -0,0 +1,60 @@
+// Copyright (C) 2020 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.gerrit.scenarios
+
+import io.gatling.core.Predef._
+import io.gatling.core.feeder.FeederBuilder
+import io.gatling.core.structure.ScenarioBuilder
+
+import scala.concurrent.duration._
+
+class FlushProjectsCache extends CacheFlushSimulation {
+  private val data: FeederBuilder = jsonFile(resource).convert(keys).queue
+  private val default: String = name
+
+  override def relativeRuntimeWeight = 2
+
+  private val flushCache: ScenarioBuilder = scenario(unique)
+      .feed(data)
+      .exec(httpRequest)
+
+  private val createProject = new CreateProject(default)
+  private val getCacheEntriesAfterProject = new GetProjectsCacheEntries(this)
+  private val checkCacheEntriesAfterFlush = new CheckProjectsCacheFlushEntries(this)
+  private val deleteProject = new DeleteProject(default)
+
+  setUp(
+    createProject.test.inject(
+      nothingFor(stepWaitTime(createProject) seconds),
+      atOnceUsers(1)
+    ),
+    getCacheEntriesAfterProject.test.inject(
+      nothingFor(stepWaitTime(getCacheEntriesAfterProject) seconds),
+      atOnceUsers(1)
+    ),
+    flushCache.inject(
+      nothingFor(stepWaitTime(this) seconds),
+      atOnceUsers(1)
+    ),
+    checkCacheEntriesAfterFlush.test.inject(
+      nothingFor(stepWaitTime(checkCacheEntriesAfterFlush) seconds),
+      atOnceUsers(1)
+    ),
+    deleteProject.test.inject(
+      nothingFor(stepWaitTime(deleteProject) seconds),
+      atOnceUsers(1)
+    ),
+  ).protocols(httpProtocol)
+}
diff --git a/e2e-tests/src/test/scala/com/google/gerrit/scenarios/GerritSimulation.scala b/e2e-tests/src/test/scala/com/google/gerrit/scenarios/GerritSimulation.scala
index 36df627..fb79f80 100644
--- a/e2e-tests/src/test/scala/com/google/gerrit/scenarios/GerritSimulation.scala
+++ b/e2e-tests/src/test/scala/com/google/gerrit/scenarios/GerritSimulation.scala
@@ -68,6 +68,8 @@
     case ("project", project) =>
       val precedes = replaceKeyWith("_project", name, project.toString)
       replaceProperty("project", precedes)
+    case ("entries", entries) =>
+      replaceProperty("projects_entries", "1", entries.toString)
   }
 
   private def replaceProperty(term: String, in: String): String = {
diff --git a/e2e-tests/src/test/scala/com/google/gerrit/scenarios/GetProjectsCacheEntries.scala b/e2e-tests/src/test/scala/com/google/gerrit/scenarios/GetProjectsCacheEntries.scala
new file mode 100644
index 0000000..27e3f19
--- /dev/null
+++ b/e2e-tests/src/test/scala/com/google/gerrit/scenarios/GetProjectsCacheEntries.scala
@@ -0,0 +1,45 @@
+// Copyright (C) 2020 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.gerrit.scenarios
+
+import io.gatling.core.Predef._
+import io.gatling.core.feeder.FeederBuilder
+import io.gatling.core.structure.ScenarioBuilder
+import io.gatling.http.Predef.{http, _}
+
+class GetProjectsCacheEntries extends CacheFlushSimulation {
+  private val data: FeederBuilder = jsonFile(resource).convert(keys).queue
+
+  def this(consumer: CacheFlushSimulation) {
+    this()
+    this.consumer = Some(consumer)
+  }
+
+  val test: ScenarioBuilder = scenario(unique)
+      .feed(data)
+      .exec(http(unique).get("${url}")
+          .check(regex("\"" + memKey + "\": (\\d+)").saveAs(entriesKey)))
+      .exec(session => {
+        if (consumer.nonEmpty) {
+          consumer.get.entriesBeforeFlush(session(entriesKey).as[Int])
+        }
+        session
+      })
+
+  setUp(
+    test.inject(
+      atOnceUsers(1)
+    )).protocols(httpProtocol)
+}
diff --git a/e2e-tests/src/test/scala/com/google/gerrit/scenarios/ReplayRecordsFromFeeder.scala b/e2e-tests/src/test/scala/com/google/gerrit/scenarios/ReplayRecordsFromFeeder.scala
index 74dc052..e5b41b3 100644
--- a/e2e-tests/src/test/scala/com/google/gerrit/scenarios/ReplayRecordsFromFeeder.scala
+++ b/e2e-tests/src/test/scala/com/google/gerrit/scenarios/ReplayRecordsFromFeeder.scala
@@ -15,13 +15,13 @@
 package com.google.gerrit.scenarios
 
 import io.gatling.core.Predef._
-import io.gatling.core.feeder.FileBasedFeederBuilder
+import io.gatling.core.feeder.FeederBuilder
 import io.gatling.core.structure.ScenarioBuilder
 
 import scala.concurrent.duration._
 
 class ReplayRecordsFromFeeder extends GitSimulation {
-  private val data: FileBasedFeederBuilder[Any]#F#F = jsonFile(resource).convert(keys).circular
+  private val data: FeederBuilder = jsonFile(resource).convert(keys).circular
   private val default: String = name
 
   override def relativeRuntimeWeight = 30
diff --git a/java/com/google/gerrit/server/restapi/account/DeleteEmail.java b/java/com/google/gerrit/server/restapi/account/DeleteEmail.java
index f690acb..5cdf4ae 100644
--- a/java/com/google/gerrit/server/restapi/account/DeleteEmail.java
+++ b/java/com/google/gerrit/server/restapi/account/DeleteEmail.java
@@ -18,6 +18,7 @@
 
 import com.google.gerrit.entities.Account;
 import com.google.gerrit.extensions.client.AccountFieldName;
+import com.google.gerrit.extensions.client.AuthType;
 import com.google.gerrit.extensions.common.Input;
 import com.google.gerrit.extensions.restapi.AuthException;
 import com.google.gerrit.extensions.restapi.MethodNotAllowedException;
@@ -33,6 +34,7 @@
 import com.google.gerrit.server.account.Realm;
 import com.google.gerrit.server.account.externalids.ExternalId;
 import com.google.gerrit.server.account.externalids.ExternalIds;
+import com.google.gerrit.server.config.AuthConfig;
 import com.google.gerrit.server.permissions.GlobalPermission;
 import com.google.gerrit.server.permissions.PermissionBackend;
 import com.google.gerrit.server.permissions.PermissionBackendException;
@@ -51,6 +53,7 @@
   private final PermissionBackend permissionBackend;
   private final AccountManager accountManager;
   private final ExternalIds externalIds;
+  private final AuthType authType;
 
   @Inject
   DeleteEmail(
@@ -58,12 +61,14 @@
       Realm realm,
       PermissionBackend permissionBackend,
       AccountManager accountManager,
-      ExternalIds externalIds) {
+      ExternalIds externalIds,
+      AuthConfig authConfig) {
     this.self = self;
     this.realm = realm;
     this.permissionBackend = permissionBackend;
     this.accountManager = accountManager;
     this.externalIds = externalIds;
+    this.authType = authConfig.getAuthType();
   }
 
   @Override
@@ -94,6 +99,14 @@
       throw new ResourceNotFoundException(email);
     }
 
+    if (realm.accountBelongsToRealm(extIds)) {
+      String errorMsg =
+          String.format(
+              "Cannot remove e-mail '%s' which is directly associated with %s authentication",
+              email, authType);
+      throw new ResourceConflictException(errorMsg);
+    }
+
     try {
       accountManager.unlink(
           user.getAccountId(), extIds.stream().map(ExternalId::key).collect(toSet()));
diff --git a/javatests/com/google/gerrit/acceptance/api/accounts/AccountIT.java b/javatests/com/google/gerrit/acceptance/api/accounts/AccountIT.java
index 18be236..d5dd241 100644
--- a/javatests/com/google/gerrit/acceptance/api/accounts/AccountIT.java
+++ b/javatests/com/google/gerrit/acceptance/api/accounts/AccountIT.java
@@ -1350,6 +1350,74 @@
   }
 
   @Test
+  @GerritConfig(name = "auth.type", value = "LDAP")
+  public void deleteEmailShouldNotRemoveLdapExternalIdScheme() throws Exception {
+    String ldapEmail = "foo@company.com";
+    String ldapExternalId = ExternalId.SCHEME_GERRIT + ":foo";
+    accountsUpdateProvider
+        .get()
+        .update(
+            "Add External IDs",
+            admin.id(),
+            u ->
+                u.addExternalId(
+                    ExternalId.createWithEmail(
+                        ExternalId.Key.parse(ldapExternalId), admin.id(), ldapEmail)));
+    assertThat(
+            gApi.accounts().self().getExternalIds().stream().map(e -> e.identity).collect(toSet()))
+        .contains(ldapExternalId);
+
+    requestScopeOperations.resetCurrentApiUser();
+    assertThat(getEmails()).contains(ldapEmail);
+
+    ResourceConflictException exception =
+        assertThrows(
+            ResourceConflictException.class, () -> gApi.accounts().self().deleteEmail(ldapEmail));
+    assertThat(exception).hasMessageThat().contains(ldapEmail);
+
+    requestScopeOperations.resetCurrentApiUser();
+    assertThat(getEmails()).contains(ldapEmail);
+    assertThat(
+            gApi.accounts().self().getExternalIds().stream().map(e -> e.identity).collect(toSet()))
+        .contains(ldapExternalId);
+  }
+
+  @Test
+  @GerritConfig(name = "auth.type", value = "LDAP")
+  public void deleteEmailShouldRemoveNonLdapExternalIdScheme() throws Exception {
+    String ldapEmail = "foo@company.com";
+    String ldapExternalId = ExternalId.SCHEME_GERRIT + ":foo";
+    String nonLdapEMail = "foo@example.com";
+    String nonLdapExternalId = ExternalId.SCHEME_MAILTO + ":foo@example.com";
+    accountsUpdateProvider
+        .get()
+        .update(
+            "Add External IDs",
+            admin.id(),
+            u ->
+                u.addExternalId(
+                        ExternalId.createWithEmail(
+                            ExternalId.Key.parse(nonLdapExternalId), admin.id(), nonLdapEMail))
+                    .addExternalId(
+                        ExternalId.createWithEmail(
+                            ExternalId.Key.parse(ldapExternalId), admin.id(), ldapEmail)));
+    assertThat(
+            gApi.accounts().self().getExternalIds().stream().map(e -> e.identity).collect(toSet()))
+        .containsAtLeast(ldapExternalId, nonLdapExternalId);
+
+    requestScopeOperations.resetCurrentApiUser();
+    assertThat(getEmails()).containsAtLeast(ldapEmail, nonLdapEMail);
+
+    gApi.accounts().self().deleteEmail(nonLdapEMail);
+
+    requestScopeOperations.resetCurrentApiUser();
+    assertThat(getEmails()).doesNotContain(nonLdapEMail);
+    assertThat(
+            gApi.accounts().self().getExternalIds().stream().map(e -> e.identity).collect(toSet()))
+        .contains(ldapExternalId);
+  }
+
+  @Test
   public void deleteEmailOfOtherUser() throws Exception {
     AccountIndexedCounter accountIndexedCounter = new AccountIndexedCounter();
     try (Registration registration =
diff --git a/resources/com/google/gerrit/httpd/auth/ldap/LoginForm.html b/resources/com/google/gerrit/httpd/auth/ldap/LoginForm.html
index 39900e8..593ea45 100644
--- a/resources/com/google/gerrit/httpd/auth/ldap/LoginForm.html
+++ b/resources/com/google/gerrit/httpd/auth/ldap/LoginForm.html
@@ -21,7 +21,7 @@
     <div id="gerrit_body" class="gerritBody">
       <h1>Sign In to Gerrit Code Review at <span id="hostName">example.com</span></h1>
       <div id="error_message">Invalid username or password.</div>
-      <form method="POST" action="#" id="login_form" onsubmit="return shouldSubmit()">
+      <form method="POST" action="#" id="login_form" autocomplete="off" onsubmit="return shouldSubmit()">
         <table style="border: 0;">
         <tr>
           <th>Username</th>