diff --git a/app/Console/Commands/BillReminder.php b/app/Console/Commands/BillReminder.php
index e06564896..02ddda567 100644
--- a/app/Console/Commands/BillReminder.php
+++ b/app/Console/Commands/BillReminder.php
@@ -78,5 +78,4 @@ class BillReminder extends Command
             }
         }
     }
-
 }
diff --git a/app/Console/Commands/InvoiceReminder.php b/app/Console/Commands/InvoiceReminder.php
index e3fcb75d9..f24fe0dc9 100644
--- a/app/Console/Commands/InvoiceReminder.php
+++ b/app/Console/Commands/InvoiceReminder.php
@@ -69,7 +69,7 @@ class InvoiceReminder extends Command
 
         foreach ($invoices as $invoice) {
             // Notify the customer
-            if ($invoice->customer) {
+            if ($invoice->customer && !empty($invoice->customer_email)) {
                 $invoice->customer->notify(new Notification($invoice));
             }
 
@@ -83,5 +83,4 @@ class InvoiceReminder extends Command
             }
         }
     }
-
 }
diff --git a/app/Http/Controllers/Auth/Users.php b/app/Http/Controllers/Auth/Users.php
index 57e75bec8..75933b591 100644
--- a/app/Http/Controllers/Auth/Users.php
+++ b/app/Http/Controllers/Auth/Users.php
@@ -243,6 +243,7 @@ class Users extends Controller
     public function autocomplete(ARequest $request)
     {
         $user = false;
+        $data = false;
 
         $column = $request['column'];
         $value = $request['value'];
@@ -250,7 +251,7 @@ class Users extends Controller
         if (!empty($column) && !empty($value)) {
             switch ($column) {
                 case 'id':
-                    $user = User::find();
+                    $user = User::find((int) $value);
                     break;
                 case 'email':
                     $user = User::where('email', $value)->first();
@@ -258,12 +259,16 @@ class Users extends Controller
                 default:
                     $user = User::where($column, $value)->first();
             }
+
+            $data = $user;
+        } elseif (!empty($column) && empty($value)) {
+            $data = trans('validation.required', ['attribute' => $column]);
         }
 
         return response()->json([
-            'errors'  => ($user) ? false: true,
-            'success' => ($user) ? true: false,
-            'data'    => $user
+            'errors'  => ($user) ? false : true,
+            'success' => ($user) ? true : false,
+            'data'    => $data
         ]);
     }
 }
diff --git a/app/Http/Controllers/Expenses/Vendors.php b/app/Http/Controllers/Expenses/Vendors.php
index 6b06d28be..90c3f8377 100644
--- a/app/Http/Controllers/Expenses/Vendors.php
+++ b/app/Http/Controllers/Expenses/Vendors.php
@@ -44,6 +44,10 @@ class Vendors extends Controller
      */
     public function store(Request $request)
     {
+        if (empty($request['email'])) {
+            $request['email'] = '';
+        }
+
         Vendor::create($request->all());
 
         $message = trans('messages.success.added', ['type' => trans_choice('general.vendors', 1)]);
@@ -120,6 +124,10 @@ class Vendors extends Controller
      */
     public function update(Vendor $vendor, Request $request)
     {
+        if (empty($request['email'])) {
+            $request['email'] = '';
+        }
+
         $vendor->update($request->all());
 
         $message = trans('messages.success.updated', ['type' => trans_choice('general.vendors', 1)]);
@@ -169,6 +177,10 @@ class Vendors extends Controller
 
     public function vendor(Request $request)
     {
+        if (empty($request['email'])) {
+            $request['email'] = '';
+        }
+
         $vendor = Vendor::create($request->all());
 
         return response()->json($vendor);
diff --git a/app/Http/Controllers/Incomes/Customers.php b/app/Http/Controllers/Incomes/Customers.php
index 17d9f1abd..ebf317aef 100644
--- a/app/Http/Controllers/Incomes/Customers.php
+++ b/app/Http/Controllers/Incomes/Customers.php
@@ -46,6 +46,10 @@ class Customers extends Controller
     public function store(Request $request)
     {
         if (empty($request->input('create_user'))) {
+            if (empty($request['email'])) {
+                $request['email'] = '';
+            }
+
             Customer::create($request->all());
         } else {
             // Check if user exist
@@ -112,6 +116,11 @@ class Customers extends Controller
 
         foreach ($rows as $row) {
             $data = $row->toArray();
+
+            if (empty($data['email'])) {
+                $data['email'] = '';
+            }
+
             $data['company_id'] = session('company_id');
 
             Customer::create($data);
@@ -149,6 +158,10 @@ class Customers extends Controller
     public function update(Customer $customer, Request $request)
     {
         if (empty($request->input('create_user'))) {
+            if (empty($request['email'])) {
+                $request['email'] = '';
+            }
+
             $customer->update($request->all());
         } else {
             // Check if user exist
@@ -220,6 +233,10 @@ class Customers extends Controller
 
     public function customer(Request $request)
     {
+        if (empty($request['email'])) {
+            $request['email'] = '';
+        }
+
         $customer = Customer::create($request->all());
 
         return response()->json($customer);
diff --git a/app/Http/Controllers/Incomes/Invoices.php b/app/Http/Controllers/Incomes/Invoices.php
index 4535a2c17..859707711 100644
--- a/app/Http/Controllers/Incomes/Invoices.php
+++ b/app/Http/Controllers/Incomes/Invoices.php
@@ -489,6 +489,10 @@ class Invoices extends Controller
      */
     public function emailInvoice(Invoice $invoice)
     {
+        if (empty($invoice->customer_email)) {
+            return redirect()->back();
+        }
+
         $invoice = $this->prepareInvoice($invoice);
 
         $logo = $this->getLogo();
diff --git a/app/Http/Requests/Expense/Vendor.php b/app/Http/Requests/Expense/Vendor.php
index b40613165..9f5e76629 100644
--- a/app/Http/Requests/Expense/Vendor.php
+++ b/app/Http/Requests/Expense/Vendor.php
@@ -23,6 +23,11 @@ class Vendor extends Request
      */
     public function rules()
     {
+        $email = '';
+
+        // Get company id
+        $company_id = $this->request->get('company_id');
+
         // Check if store or update
         if ($this->getMethod() == 'PATCH') {
             $id = $this->vendor->getAttribute('id');
@@ -30,12 +35,13 @@ class Vendor extends Request
             $id = null;
         }
 
-        // Get company id
-        $company_id = $this->request->get('company_id');
+        if (!empty($this->request->get('email'))) {
+            $email = 'email|unique:vendors,NULL,' . $id . ',id,company_id,' . $company_id . ',deleted_at,NULL';
+        }
 
         return [
             'name' => 'required|string',
-            'email' => 'required|email|unique:vendors,NULL,' . $id . ',id,company_id,' . $company_id . ',deleted_at,NULL',
+            'email' => $email,
             'currency_code' => 'required|string',
         ];
     }
diff --git a/app/Http/Requests/Income/Customer.php b/app/Http/Requests/Income/Customer.php
index 861524f9c..4d2e97622 100644
--- a/app/Http/Requests/Income/Customer.php
+++ b/app/Http/Requests/Income/Customer.php
@@ -23,8 +23,12 @@ class Customer extends Request
      */
     public function rules()
     {
+        $email = '';
         $required = '';
 
+        // Get company id
+        $company_id = $this->request->get('company_id');
+
         // Check if store or update
         if ($this->getMethod() == 'PATCH') {
             $id = $this->customer->getAttribute('id');
@@ -36,12 +40,13 @@ class Customer extends Request
             $required = 'required|';
         }
 
-        // Get company id
-        $company_id = $this->request->get('company_id');
+        if (!empty($this->request->get('email'))) {
+            $email = 'email|unique:customers,NULL,' . $id . ',id,company_id,' . $company_id . ',deleted_at,NULL';
+        }
 
         return [
             'name' => 'required|string',
-            'email' => 'required|email|unique:customers,NULL,' . $id . ',id,company_id,' . $company_id . ',deleted_at,NULL',
+            'email' => $email,
             'currency_code' => 'required|string',
             'password' => $required . 'confirmed',
         ];
diff --git a/public/css/app.css b/public/css/app.css
index 78f922c22..cb55b99af 100644
--- a/public/css/app.css
+++ b/public/css/app.css
@@ -498,6 +498,18 @@ ul.add-new.nav.navbar-nav.pull-left {
         background-color: #ffffff;
     }
 }
+
+.text-disabled {
+    opacity: 0.4;
+}
+
+.tooltip > .tooltip-inner {
+    background-color: #6da252;
+}
+
+.tooltip.right .tooltip-arrow {
+    border-right-color: #6da252 !important;
+}
 /*
 .content-wrapper {
     overflow: inherit;
diff --git a/resources/lang/en-GB/invoices.php b/resources/lang/en-GB/invoices.php
index 7f52a170f..d1a62106d 100644
--- a/resources/lang/en-GB/invoices.php
+++ b/resources/lang/en-GB/invoices.php
@@ -37,8 +37,9 @@ return [
     ],
 
     'messages' => [
-        'email_sent'    => 'Invoice email has been sent successfully!',
-        'marked_sent'   => 'Invoice marked as sent successfully!',
+        'email_sent'     => 'Invoice email has been sent successfully!',
+        'marked_sent'    => 'Invoice marked as sent successfully!',
+        'email_required' => 'No email address for this customer!',
     ],
 
     'notification' => [
diff --git a/resources/views/expenses/bills/create.blade.php b/resources/views/expenses/bills/create.blade.php
index 8b897a4bb..c46071d5f 100644
--- a/resources/views/expenses/bills/create.blade.php
+++ b/resources/views/expenses/bills/create.blade.php
@@ -290,7 +290,7 @@
             modal += '                          <input class="form-control" placeholder="{{ trans('general.name') }}" required="required" name="name" type="text" id="name">';
             modal += '                      </div>';
             modal += '                  </div>';
-            modal += '                  <div class="form-group col-md-6 required">';
+            modal += '                  <div class="form-group col-md-6">';
             modal += '                      <label for="email" class="control-label">{{ trans('general.email') }}</label>';
             modal += '                      <div class="input-group">';
             modal += '                          <div class="input-group-addon"><i class="fa fa-envelope"></i></div>';
diff --git a/resources/views/expenses/vendors/create.blade.php b/resources/views/expenses/vendors/create.blade.php
index f6d8c65fc..fd0f12fb2 100644
--- a/resources/views/expenses/vendors/create.blade.php
+++ b/resources/views/expenses/vendors/create.blade.php
@@ -10,7 +10,7 @@
         <div class="box-body">
             {{ Form::textGroup('name', trans('general.name'), 'id-card-o') }}
 
-            {{ Form::textGroup('email', trans('general.email'), 'envelope') }}
+            {{ Form::textGroup('email', trans('general.email'), 'envelope', []) }}
 
             {{ Form::textGroup('tax_number', trans('general.tax_number'), 'percent', []) }}
 
diff --git a/resources/views/expenses/vendors/edit.blade.php b/resources/views/expenses/vendors/edit.blade.php
index 32c7ca5ab..082969e78 100644
--- a/resources/views/expenses/vendors/edit.blade.php
+++ b/resources/views/expenses/vendors/edit.blade.php
@@ -14,7 +14,7 @@
         <div class="box-body">
             {{ Form::textGroup('name', trans('general.name'), 'id-card-o') }}
 
-            {{ Form::textGroup('email', trans('general.email'), 'envelope') }}
+            {{ Form::textGroup('email', trans('general.email'), 'envelope', []) }}
 
             {{ Form::textGroup('tax_number', trans('general.tax_number'), 'percent', []) }}
 
diff --git a/resources/views/expenses/vendors/index.blade.php b/resources/views/expenses/vendors/index.blade.php
index ffb3bc589..50bb5be2e 100644
--- a/resources/views/expenses/vendors/index.blade.php
+++ b/resources/views/expenses/vendors/index.blade.php
@@ -43,7 +43,7 @@
                 @foreach($vendors as $item)
                     <tr>
                         <td><a href="{{ url('expenses/vendors/' . $item->id . '/edit') }}">{{ $item->name }}</a></td>
-                        <td class="hidden-xs">{{ $item->email }}</td>
+                        <td class="hidden-xs">{{ !empty($item->email) ? $item->email : 'N/A'}}</td>
                         <td>{{ $item->phone }}</td>
                         <td class="hidden-xs">
                             @if ($item->enabled)
diff --git a/resources/views/incomes/customers/create.blade.php b/resources/views/incomes/customers/create.blade.php
index e0cd1a24d..264da5a3f 100644
--- a/resources/views/incomes/customers/create.blade.php
+++ b/resources/views/incomes/customers/create.blade.php
@@ -10,7 +10,7 @@
         <div class="box-body">
             {{ Form::textGroup('name', trans('general.name'), 'id-card-o') }}
 
-            {{ Form::textGroup('email', trans('general.email'), 'envelope') }}
+            {{ Form::textGroup('email', trans('general.email'), 'envelope', []) }}
 
             {{ Form::textGroup('tax_number', trans('general.tax_number'), 'percent', []) }}
 
@@ -68,7 +68,7 @@
             $('#create_user').iCheck({
                 checkboxClass: 'icheckbox_square-green',
                 radioClass: 'iradio_square-green',
-                increaseArea: '20%' // optional
+                increaseArea: '20%'
             });
 
             $('#create_user').on('ifClicked', function (event) {
@@ -76,13 +76,29 @@
 
                 if ($(this).prop('checked')) {
                     $('.col-md-6.password').addClass('hidden');
+
+                    $('input[name="email"]').parent().parent().removeClass('has-error');
+                    $('input[name="email"]').parent().parent().find('.help-block').remove();
                 } else {
+                    var email = $('input[name="email"]').val();
+
+                    if (!email) {
+                        $('input[name="email"]').parent().parent().addClass('has-error');
+                        $('input[name="email"]').parent().after('<p class="help-block">{{ trans('validation.required', ['attribute' => 'email']) }}</p>');
+                        $('input[name="email"]').focus();
+
+                        return false;
+                    }
+
                     $.ajax({
                         url: '{{ url("auth/users/autocomplete") }}',
                         type: 'GET',
                         dataType: 'JSON',
-                        data: {column: 'email', value: $('input[name="email"]').val()},
+                        data: {column: 'email', value: email},
                         beforeSend: function() {
+                            $('input[name="email"]').parent().parent().removeClass('has-error');
+                            $('input[name="email"]').parent().parent().find('.help-block').remove();
+
                             $('.box-footer .btn').attr('disabled', true);
                         },
                         complete: function() {
@@ -90,6 +106,14 @@
                         },
                         success: function(json) {
                             if (json['errors']) {
+                                if (json['data']) {
+                                    $('input[name="email"]').parent().parent().addClass('has-error');
+                                    $('input[name="email"]').parent().after('<p class="help-block">' + json['data'] + '</p>');
+                                    $('input[name="email"]').focus();
+
+                                    return false;
+                                }
+
                                 $('.col-md-6.password').removeClass('hidden');
                             }
 
diff --git a/resources/views/incomes/customers/edit.blade.php b/resources/views/incomes/customers/edit.blade.php
index 739af59f8..8d7ed7429 100644
--- a/resources/views/incomes/customers/edit.blade.php
+++ b/resources/views/incomes/customers/edit.blade.php
@@ -14,7 +14,7 @@
     <div class="box-body">
         {{ Form::textGroup('name', trans('general.name'), 'id-card-o') }}
 
-        {{ Form::textGroup('email', trans('general.email'), 'envelope') }}
+        {{ Form::textGroup('email', trans('general.email'), 'envelope', []) }}
 
         {{ Form::textGroup('tax_number', trans('general.tax_number'), 'percent', []) }}
 
diff --git a/resources/views/incomes/customers/index.blade.php b/resources/views/incomes/customers/index.blade.php
index 2edd47f10..2b09b68c3 100644
--- a/resources/views/incomes/customers/index.blade.php
+++ b/resources/views/incomes/customers/index.blade.php
@@ -43,7 +43,7 @@
                 @foreach($customers as $item)
                     <tr>
                         <td><a href="{{ url('incomes/customers/' . $item->id . '/edit') }}">{{ $item->name }}</a></td>
-                        <td class="hidden-xs">{{ $item->email }}</td>
+                        <td class="hidden-xs">{{ !empty($item->email) ? $item->email : 'N/A'}}</td>
                         <td>{{ $item->phone }}</td>
                         <td class="hidden-xs">
                             @if ($item->enabled)
diff --git a/resources/views/incomes/invoices/create.blade.php b/resources/views/incomes/invoices/create.blade.php
index fcfdccb58..cff4e31aa 100644
--- a/resources/views/incomes/invoices/create.blade.php
+++ b/resources/views/incomes/invoices/create.blade.php
@@ -291,7 +291,7 @@
             modal += '                          <input class="form-control" placeholder="{{ trans('general.name') }}" required="required" name="name" type="text" id="name">';
             modal += '                      </div>';
             modal += '                  </div>';
-            modal += '                  <div class="form-group col-md-6 required">';
+            modal += '                  <div class="form-group col-md-6">';
             modal += '                      <label for="email" class="control-label">{{ trans('general.email') }}</label>';
             modal += '                      <div class="input-group">';
             modal += '                          <div class="input-group-addon"><i class="fa fa-envelope"></i></div>';
diff --git a/resources/views/incomes/invoices/show.blade.php b/resources/views/incomes/invoices/show.blade.php
index cb3516688..d06f5d071 100644
--- a/resources/views/incomes/invoices/show.blade.php
+++ b/resources/views/incomes/invoices/show.blade.php
@@ -163,7 +163,11 @@
                             @permission('update-incomes-invoices')
                             <li><a href="{{ url('incomes/invoices/' . $invoice->id . '/sent') }}">{{ trans('invoices.mark_sent') }}</a></li>
                             @endpermission
+                            @if($invoice->customer_email)
                             <li><a href="{{ url('incomes/invoices/' . $invoice->id . '/email') }}">{{ trans('invoices.send_mail') }}</a></li>
+                            @else
+                            <li><a href="javascript:void(0);" class="green-tooltip disabled" data-toggle="tooltip" data-placement="right" title="{{ trans('invoices.messages.email_required') }}"><span class="text-disabled">{{ trans('invoices.send_mail') }}</span></a></li>
+                            @endif
                             <li class="divider"></li>
                             <li><a href="{{ url('incomes/invoices/' . $invoice->id . '/pdf') }}">{{ trans('invoices.download_pdf') }}</a></li>
                             <li class="divider"></li>