--- a/mail/themes/osx/mail/compose/messengercompose.css
+++ b/mail/themes/osx/mail/compose/messengercompose.css
@@ -435,45 +435,43 @@ toolbar[mode="icons"] .toolbarbutton-1 >
 /* ::::: special toolbar colors ::::: */
 
 #composeContentBox {
   box-shadow: 0px 2px 4px rgba(0, 0, 0, 0.6) inset;
   background-color: rgb(242, 242, 242);
 
   /*
    * In order to remove the shadow border on left/right edges elegantly,
-   * use left/right margins of -3px. Just note that certain elements might need
-   * a margin-left or margin-right change.
+   * use left/right margins of -3px. We make up for this by adding 3px
+   * of padding instead.
    */
 
   margin-right: -3px;
   margin-left: -3px;
+  padding-right: 3px;
+  padding-left: 3px;
 }
 
 #composeContentBox:-moz-window-inactive {
   box-shadow: 0px 1px 2px rgba(0, 0, 0, 0.2) inset;
 }
 
-#content-frame {
-  -moz-margin-end: 3px;
-}
-
-#attachments-box {
-  -moz-padding-end: 3px;
+#headers-box {
+  padding-top: 5px;
 }
 
 #MsgHeadersToolbar {
   color: -moz-DialogText;
   text-shadow: none;
   background-image: url("chrome://messenger/skin/noise.png");
   border-bottom: 0px solid;
 }
 
 #msgIdentity {
-   -moz-margin-start: 0px;
+   margin: 0px;
    -moz-padding-start: 3px;
    background: transparent;
    line-height: 1;
    border: 1px solid transparent;
    border-bottom: 1px solid #C6C6C6;
    border-radius: 0;
    -moz-appearance: none;
    background: url("chrome://global/skin/arrow/arrow-dn.gif") no-repeat right;
@@ -488,17 +486,16 @@ toolbar[mode="icons"] .toolbarbutton-1 >
 #addresses-box {
   margin: 4px 6px;
 }
 
 #attachmentbucket-sizer {
   border-top: none;
   border-bottom: none;
   height: 7px;
-  -moz-margin-end: 3px;
 }
 
 #attachmentBucketSize {
   color: #888a85;
 }
 
 /* ::::: attachment reminder ::::: */
 
@@ -527,16 +524,17 @@ toolbar[mode="icons"] .toolbarbutton-1 >
   margin-top: 2px;
 }
 
 #subject-box {
   -moz-margin-start: -2px;
 }
 
 #msgSubject {
+  margin-top: 0px;
   -moz-margin-start: 2px;
   -moz-margin-end: 1px;
   background-color: inherit;
   -moz-appearance: none !important;
   border-top: 1px solid transparent;
   border-left: 1px solid transparent;
   border-right: 1px solid transparent;
   border-bottom: 1px solid #C6C6C6;
@@ -621,17 +619,17 @@ treechildren::-moz-tree-image(subscribed
 }
 
 /* ::::: addressing widget ::::: */
 
 #addressingWidget {
   -moz-user-focus: none;
   -moz-appearance: none;
   width: 0;
-  margin: 5px 0px;
+  margin: 0px;
   border: none;
   background-color: transparent;
 }
 
 #addressingWidget listboxbody {
   margin: 1px 0;
   background-color: transparent;
 }
@@ -643,16 +641,18 @@ treechildren::-moz-tree-image(subscribed
 }
 
 .textbox-addressingWidget,
 .dummy-row-cell:not(:first-child) {
   border-top: 1px solid transparent !important;
   border-left: 1px solid transparent !important;
   border-right: 1px solid transparent !important;
   border-bottom: 1px solid #C6C6C6 !important;
+  border-top-right-radius: 0px;
+  border-bottom-left-radius: 0px;
   padding: 2px !important;
 
   transition: border .2s, background-color .2s;
 }
 
 .textbox-addressingWidget[focused="true"],
 .textbox-addressingWidget:hover {
   background-color: white;
@@ -683,30 +683,33 @@ treechildren::-moz-tree-image(subscribed
   margin: 0 1px !important;
   font-size: 10px;
   text-align: start;
 }
 
 /* ::::: compose toolbar sizer ::::: */
 
 #compose-toolbar-sizer {
+  position: relative;
+  margin-top: -2px;
+  min-height: 7px;
   background-image: url("chrome://messenger/skin/messengercompose/osx-noise.png");
   background-color: rgb(242, 242, 242);
   border-bottom: 1px solid #DCDCDC;
 }
 
 /* ::::: format toolbar ::::: */
 
 #FormatToolbar {
   border-bottom: none;
   background-image: url("chrome://messenger/skin/messengercompose/osx-noise.png");
   background-color: rgb(242, 242, 242) !important;
   padding-top: 2px;
-  margin-left: 6px;
-  margin-right: 6px;
+  margin-left: 3px;
+  margin-right: 3px;
 }
 
 #FormatToolbar toolbarseparator {
   background-image: none;
 }
 
 toolbarbutton.formatting-button {
   -moz-appearance: toolbarbutton;