diff --git a/src/app/Backends/LDAP.php b/src/app/Backends/LDAP.php
--- a/src/app/Backends/LDAP.php
+++ b/src/app/Backends/LDAP.php
@@ -954,7 +954,12 @@
     {
         $settings = $group->getSettings(['sender_policy']);
 
-        $entry['kolaballowsmtpsender'] = json_decode($settings['sender_policy'] ?: '[]', true);
+        // Make sure the policy does not contain duplicates, they aren't allowed
+        // by the ldap definition of kolabAllowSMTPSender attribute
+        $sender_policy = json_decode($settings['sender_policy'] ?: '[]', true);
+        $sender_policy = array_values(array_unique(array_map('strtolower', $sender_policy)));
+
+        $entry['kolaballowsmtpsender'] = $sender_policy;
         $entry['cn'] = $group->name;
         $entry['uniquemember'] = [];
 
diff --git a/src/app/Console/Commands/Group/ResyncCommand.php b/src/app/Console/Commands/Group/ResyncCommand.php
new file mode 100644
--- /dev/null
+++ b/src/app/Console/Commands/Group/ResyncCommand.php
@@ -0,0 +1,110 @@
+<?php
+
+namespace App\Console\Commands\Group;
+
+use App\Console\Command;
+use App\Group;
+
+class ResyncCommand extends Command
+{
+    /**
+     * The name and signature of the console command.
+     *
+     * @var string
+     */
+    protected $signature = 'group:resync {group?} {--deleted-only} {--dry-run}';
+
+    /**
+     * The console command description.
+     *
+     * @var string
+     */
+    protected $description = "Re-Synchronize groups with the imap/ldap backend(s)";
+
+    /**
+     * Execute the console command.
+     *
+     * @return mixed
+     */
+    public function handle()
+    {
+        $group = $this->argument('group');
+        $deleted_only = $this->option('deleted-only');
+        $dry_run = $this->option('dry-run');
+        $with_ldap = \config('app.with_ldap');
+
+        if (!empty($group)) {
+            if ($req_group = $this->getGroup($group, true)) {
+                $groups = [$req_group];
+            } else {
+                $this->error("Group not found.");
+                return 1;
+            }
+        } else {
+            $groups = Group::withTrashed();
+
+            if ($deleted_only) {
+                $groups->whereNotNull('deleted_at')
+                    ->where(function ($query) {
+                        $query->where('status', '&', Group::STATUS_LDAP_READY);
+                    });
+            }
+
+            $groups = $groups->orderBy('id')->cursor();
+        }
+
+        // TODO: Maybe we should also have account:resync, domain:resync, resource:resync and so on.
+
+        foreach ($groups as $group) {
+            if ($group->trashed()) {
+                if ($with_ldap && $group->isLdapReady()) {
+                    if ($dry_run) {
+                        $this->info("{$group->email}: will be pushed");
+                        continue;
+                    }
+
+                    if ($group->isDeleted()) {
+                        // Remove the DELETED flag so the DeleteJob can do the work
+                        $group->timestamps = false;
+                        $group->update(['status' => $group->status ^ Group::STATUS_DELETED]);
+                    }
+
+                    // TODO: Do this not asyncronously as an option or when a signle group is requested?
+                    \App\Jobs\Group\DeleteJob::dispatch($group->id);
+
+                    $this->info("{$group->email}: pushed");
+                } else {
+                    // Group properly deleted, no need to push.
+                    // Here potentially we could connect to ldap/imap backend and check to be sure
+                    // that the group is really deleted no matter what status it has in the database.
+
+                    $this->info("{$group->email}: in-sync");
+                }
+            } else {
+                if (!$group->isActive() || ($with_ldap && !$group->isLdapReady())) {
+                    if ($dry_run) {
+                        $this->info("{$group->email}: will be pushed");
+                        continue;
+                    }
+
+                    \App\Jobs\Group\CreateJob::dispatch($group->id);
+
+                    $this->info("{$group->email}: pushed");
+                } elseif (!empty($req_group)) {
+                    if ($dry_run) {
+                        $this->info("{$group->email}: will be pushed");
+                        continue;
+                    }
+
+                    // We push the update only if a specific group is requested,
+                    // We don't want to flood the database/backend with an update of all groups
+                    \App\Jobs\Group\UpdateJob::dispatch($group->id);
+
+                    $this->info("{$group->email}: pushed");
+                } else {
+                    $this->info("{$group->email}: in-sync");
+                }
+            }
+        }
+    }
+}
diff --git a/src/app/Console/Commands/User/ResyncCommand.php b/src/app/Console/Commands/User/ResyncCommand.php
--- a/src/app/Console/Commands/User/ResyncCommand.php
+++ b/src/app/Console/Commands/User/ResyncCommand.php
@@ -89,6 +89,8 @@
                     }
 
                     \App\Jobs\User\CreateJob::dispatch($user->id);
+
+                    $this->info("{$user->email}: pushed");
                 } elseif (!empty($req_user)) {
                     if ($dry_run) {
                         $this->info("{$user->email}: will be pushed");
diff --git a/src/tests/Feature/Backends/LDAPTest.php b/src/tests/Feature/Backends/LDAPTest.php
--- a/src/tests/Feature/Backends/LDAPTest.php
+++ b/src/tests/Feature/Backends/LDAPTest.php
@@ -163,13 +163,13 @@
         // Update members
         $group->members = ['member3@testldap.com'];
         $group->save();
-        $group->setSetting('sender_policy', '["test.com","-"]');
+        $group->setSetting('sender_policy', '["test.com","Test.com","-"]');
 
         LDAP::updateGroup($group);
 
         // TODO: Should we force this to be always an array?
         $expected['uniquemember'] = 'uid=member3@testldap.com,ou=People,ou=kolab.org,' . $root_dn;
-        $expected['kolaballowsmtpsender'] = ['test.com', '-'];
+        $expected['kolaballowsmtpsender'] = ['test.com', '-']; // duplicates removed
 
         $ldap_group = LDAP::getGroup($group->email);