diff --git a/addons/mail/static/src/components/attachment_viewer/attachment_viewer.scss b/addons/mail/static/src/components/attachment_viewer/attachment_viewer.scss
index 689ae09abcf..b5769565a55 100644
--- a/addons/mail/static/src/components/attachment_viewer/attachment_viewer.scss
+++ b/addons/mail/static/src/components/attachment_viewer/attachment_viewer.scss
@@ -32,19 +32,6 @@
     min-width: 0;
 }
 
-.o_AttachmentViewer_toolbar {
-    bottom: $o-navbar-height * 1.125;
-    transform: translateY(100%);
-}
-
-.o_AttachmentViewer_toolbarButton {
-    padding: 8px;
-}
-
-.o_AttachmentViewer_viewIframe {
-    width: 90%;
-}
-
 .o_AttachmentViewer_zoomer {
     padding: ($o-navbar-height * 1.125) 0;
 }
@@ -57,35 +44,13 @@
     outline: none;
 }
 
-.o_AttachmentViewer_buttonNavigation {
-    color: gray('400');
-    background-color: lighten($black, 15%);
-
-    &:hover {
-        color: lighten(gray('400'), 15%);
-        background-color: $black;
-    }
-}
-
 .o_AttachmentViewer_headerItemButton:hover {
     background-color: rgba($white, 0.1);
     color: lighten($gray-400, 15%);
 }
 
-.o_AttachmentViewer_toolbarButton {
-    background-color: lighten($black, 15%);
-
-    &.o_disabled {
-        filter: brightness(1.3);
-    }
-
-    &:not(.o_disabled) {
-        @include o-hover-text-color($gray-400, lighten($gray-400, 15%));
-
-        &:hover {
-            background-color: $black;
-        }
-    }
+.o_AttachmentViewer_toolbarButton.o_disabled {
+    filter: brightness(1.3);
 }
 
 .o_AttachmentViewer_view {
diff --git a/addons/mail/static/src/components/attachment_viewer/attachment_viewer.xml b/addons/mail/static/src/components/attachment_viewer/attachment_viewer.xml
index 52778243e1c..c8ca26fc17e 100644
--- a/addons/mail/static/src/components/attachment_viewer/attachment_viewer.xml
+++ b/addons/mail/static/src/components/attachment_viewer/attachment_viewer.xml
@@ -47,13 +47,13 @@
                         </div>
                     </t>
                     <t t-if="attachmentViewer.attachment.isPdf">
-                        <iframe class="o_AttachmentViewer_view o_AttachmentViewer_viewIframe o_AttachmentViewer_viewPdf h-100 bg-black border-0" t-ref="iframeViewerPdf" t-att-class="{ 'o-isMobile w-100': messaging.device.isMobile }" t-att-src="attachmentViewer.attachment.defaultSource"/>
+                        <iframe class="o_AttachmentViewer_view o_AttachmentViewer_viewIframe o_AttachmentViewer_viewPdf w-75 h-100 bg-black border-0" t-ref="iframeViewerPdf" t-att-class="{ 'o-isMobile w-100': messaging.device.isMobile }" t-att-src="attachmentViewer.attachment.defaultSource"/>
                     </t>
                     <t t-if="attachmentViewer.attachment.isText">
-                        <iframe class="o_AttachmentViewer_view o_AttachmentViewer_viewIframe o_text h-100 bg-white border-0" t-att-src="attachmentViewer.attachment.defaultSource"/>
+                        <iframe class="o_AttachmentViewer_view o_AttachmentViewer_viewIframe o_text w-75 h-100 bg-white border-0" t-att-src="attachmentViewer.attachment.defaultSource"/>
                     </t>
                     <t t-if="attachmentViewer.attachment.isUrlYoutube">
-                        <iframe allow="autoplay; encrypted-media" class="o_AttachmentViewer_view o_AttachmentViewer_viewIframe o_AttachmentViewer_youtube h-100 bg-black border-0" t-att-src="attachmentViewer.attachment.defaultSource" height="315" width="560"/>
+                        <iframe allow="autoplay; encrypted-media" class="o_AttachmentViewer_view o_AttachmentViewer_viewIframe o_AttachmentViewer_youtube w-75 h-100 bg-black border-0" t-att-src="attachmentViewer.attachment.defaultSource" height="315" width="560"/>
                     </t>
                     <t t-if="attachmentViewer.attachment.isVideo">
                         <video class="o_AttachmentViewer_view o_AttachmentViewer_viewVideo w-75 h-75 bg-black" t-att-class="{ 'o-isMobile w-100 h-100': messaging.device.isMobile }" t-on-click="_onClickVideo" controls="controls">
@@ -62,32 +62,32 @@
                     </t>
                 </div>
                 <t t-if="attachmentViewer.attachment.isImage">
-                    <div class="o_AttachmentViewer_toolbar position-absolute d-flex" role="toolbar">
-                        <div class="o_AttachmentViewer_toolbarButton o_cursor_pointer" t-on-click="_onClickZoomIn" title="Zoom In (+)" role="button">
+                    <div class="o_AttachmentViewer_toolbar position-absolute bottom-0 d-flex" role="toolbar">
+                        <div class="o_AttachmentViewer_toolbarButton btn btn-dark p-3 rounded-0" t-on-click="_onClickZoomIn" title="Zoom In (+)" role="button">
                             <i class="fa fa-fw fa-plus" role="img"/>
                         </div>
-                        <div class="o_AttachmentViewer_toolbarButton o_cursor_pointer" t-att-class="{ o_disabled: attachmentViewer.scale === 1 }" t-on-click="_onClickZoomReset" role="button" title="Reset Zoom (0)">
+                        <div class="o_AttachmentViewer_toolbarButton btn btn-dark p-3 rounded-0" t-att-class="{ o_disabled: attachmentViewer.scale === 1 }" t-on-click="_onClickZoomReset" role="button" title="Reset Zoom (0)">
                             <i class="fa fa-fw fa-search" role="img"/>
                         </div>
-                        <div class="o_AttachmentViewer_toolbarButton o_cursor_pointer" t-att-class="{ o_disabled: attachmentViewer.scale === MIN_SCALE }" t-on-click="_onClickZoomOut" title="Zoom Out (-)" role="button">
+                        <div class="o_AttachmentViewer_toolbarButton btn btn-dark p-3 rounded-0" t-att-class="{ o_disabled: attachmentViewer.scale === MIN_SCALE }" t-on-click="_onClickZoomOut" title="Zoom Out (-)" role="button">
                             <i class="fa fa-fw fa-minus" role="img"/>
                         </div>
-                        <div class="o_AttachmentViewer_toolbarButton o_cursor_pointer" t-on-click="_onClickRotate" title="Rotate (r)" role="button">
+                        <div class="o_AttachmentViewer_toolbarButton btn btn-dark p-3 rounded-0" t-on-click="_onClickRotate" title="Rotate (r)" role="button">
                             <i class="fa fa-fw fa-repeat" role="img"/>
                         </div>
-                        <div class="o_AttachmentViewer_toolbarButton o_cursor_pointer" t-on-click="_onClickPrint" title="Print" role="button">
+                        <div class="o_AttachmentViewer_toolbarButton btn btn-dark p-3 rounded-0" t-on-click="_onClickPrint" title="Print" role="button">
                             <i class="fa fa-fw fa-print" role="img"/>
                         </div>
-                        <div class="o_AttachmentViewer_buttonDownload o_AttachmentViewer_toolbarButton o_cursor_pointer" t-on-click="_onClickDownload" title="Download" role="button">
+                        <div class="o_AttachmentViewer_buttonDownload o_AttachmentViewer_toolbarButton btn btn-dark p-3 rounded-0 o_cursor_pointer" t-on-click="_onClickDownload" title="Download" role="button">
                             <i class="fa fa-download fa-fw" role="img"/>
                         </div>
                     </div>
                 </t>
                 <t t-if="attachmentViewer.attachments.length > 1">
-                    <div class="o_AttachmentViewer_buttonNavigation o_AttachmentViewer_buttonNavigationPrevious o_AttachmentViewer_buttonNavigationPreviousIcon btn position-absolute top-0 bottom-0 start-0 align-items-center justify-content-center d-flex my-auto ms-3 rounded-circle text-400" t-on-click="_onClickPrevious" title="Previous (Left-Arrow)" role="button">
+                    <div class="o_AttachmentViewer_buttonNavigation o_AttachmentViewer_buttonNavigationPrevious o_AttachmentViewer_buttonNavigationPreviousIcon btn btn-dark position-absolute top-0 bottom-0 start-0 align-items-center justify-content-center d-flex my-auto ms-3 rounded-circle" t-on-click="_onClickPrevious" title="Previous (Left-Arrow)" role="button">
                         <span class="fa fa-chevron-left" role="img"/>
                     </div>
-                    <div class="o_AttachmentViewer_buttonNavigation o_AttachmentViewer_buttonNavigationNext o_AttachmentViewer_buttonNavigationNextIcon btn position-absolute top-0 bottom-0 end-0 align-items-center justify-content-center d-flex my-auto me-3 rounded-circle text-400" t-on-click="_onClickNext" title="Next (Right-Arrow)" role="button">
+                    <div class="o_AttachmentViewer_buttonNavigation o_AttachmentViewer_buttonNavigationNext o_AttachmentViewer_buttonNavigationNextIcon btn btn-dark position-absolute top-0 bottom-0 end-0 align-items-center justify-content-center d-flex my-auto me-3 rounded-circle" t-on-click="_onClickNext" title="Next (Right-Arrow)" role="button">
                         <span class="fa fa-chevron-right" role="img"/>
                     </div>
                 </t>