--- a/mail/themes/linux/jar.mn
+++ b/mail/themes/linux/jar.mn
@@ -186,17 +186,16 @@ classic.jar:
   skin/classic/messenger/icons/filterbar.png                  (mail/icons/filterbar.png)
   skin/classic/messenger/icons/red_pin.png                    (mail/icons/red_pin.png)
   skin/classic/messenger/tabs/active-middle.png               (mail/tabs/active-middle.png)
   skin/classic/messenger/tabs/background-end.png              (mail/tabs/background-end.png)
   skin/classic/messenger/tabs/background-middle.png           (mail/tabs/background-middle.png)
   skin/classic/messenger/tabs/background-start.png            (mail/tabs/background-start.png)
   skin/classic/messenger/tabs/selected-end.svg                (mail/tabs/selected-end.svg)
   skin/classic/messenger/tabs/selected-start.svg              (mail/tabs/selected-start.svg)
-  skin/classic/messenger/tabs/separator.png                   (mail/tabs/separator.png)
   skin/classic/messenger/tabs/stroke-end.png                  (mail/tabs/stroke-end.png)
   skin/classic/messenger/tabs/stroke-start.png                (mail/tabs/stroke-start.png)
   skin/classic/messenger/tabs/dragIndicator.png               (mail/tabs/dragIndicator.png)
   skin/classic/messenger/tabs/overflow-indicator.png          (mail/tabs/overflow-indicator.png)
   skin/classic/messenger/icons/chat-toolbar.svg               (../shared/mail/icons/chat-toolbar.svg)
   skin/classic/messenger/icons/status.png                     (mail/icons/status.png)
   skin/classic/messenger/icons/status-small.png               (mail/icons/status-small.png)
 % skin communicator classic/1.0 %skin/classic/communicator/

deleted file mode 100644
index 0b3c4e4b5f6957c906c13ca2e73d11c523649441..0000000000000000000000000000000000000000
GIT binary patch
literal 0
Hc$@<O00001

--- a/mail/themes/osx/jar.mn
+++ b/mail/themes/osx/jar.mn
@@ -262,18 +262,16 @@ classic.jar:
   skin/classic/messenger/tabs/background-end@2x.png              (mail/tabs/background-end@2x.png)
   skin/classic/messenger/tabs/background-middle.png              (mail/tabs/background-middle.png)
   skin/classic/messenger/tabs/background-middle@2x.png           (mail/tabs/background-middle@2x.png)
   skin/classic/messenger/tabs/background-start.png               (mail/tabs/background-start.png)
   skin/classic/messenger/tabs/background-start@2x.png            (mail/tabs/background-start@2x.png)
   skin/classic/messenger/tabs/overflow-indicator.png             (mail/tabs/overflow-indicator.png)
   skin/classic/messenger/tabs/selected-end.svg                   (mail/tabs/selected-end.svg)
   skin/classic/messenger/tabs/selected-start.svg                 (mail/tabs/selected-start.svg)
-  skin/classic/messenger/tabs/separator.png                      (mail/tabs/separator.png)
-  skin/classic/messenger/tabs/separator@2x.png                   (mail/tabs/separator@2x.png)
   skin/classic/messenger/tabs/stroke-end.png                     (mail/tabs/stroke-end.png)
   skin/classic/messenger/tabs/stroke-end@2x.png                  (mail/tabs/stroke-end@2x.png)
   skin/classic/messenger/tabs/stroke-start.png                   (mail/tabs/stroke-start.png)
   skin/classic/messenger/tabs/stroke-start@2x.png                (mail/tabs/stroke-start@2x.png)
   skin/classic/messenger/accountcentral/accountsettings.png      (mail/accountcentral/accountsettings.png)
   skin/classic/messenger/accountcentral/accountsettings@2x.png   (mail/accountcentral/accountsettings@2x.png)
   skin/classic/messenger/accountcentral/folder.png               (mail/accountcentral/folder.png)
   skin/classic/messenger/accountcentral/folder@2x.png            (mail/accountcentral/folder@2x.png)

--- a/mail/themes/osx/mail/tabmail.css
+++ b/mail/themes/osx/mail/tabmail.css
@@ -68,21 +68,16 @@
     background-image: url(tabs/stroke-start@2x.png);
   }
 
   .tab-background-end[selected=true]:-moz-locale-dir(ltr)::after,
   .tab-background-start[selected=true]:-moz-locale-dir(rtl)::after {
     background-image: url(tabs/stroke-end@2x.png);
   }
 
-  /* Background tab separators */
-  #tabs-toolbar:not([brighttext]) {
-    --tab-separator-image: url(chrome://browser/skin/tabbrowser/tab-separator@2x.png);
-  }
-
   .tab-throbber {
     list-style-image: url("chrome://messenger/skin/icons/loading@2x.png") !important;
   }
 
   .tabmail-tab[type="glodaSearch"] {
     list-style-image: url("chrome://messenger/skin/icons/search-tab@2x.png");
   }
 }

deleted file mode 100644
index b81e691acd2c1d3027ec3675c5e189571f488ad4..0000000000000000000000000000000000000000
GIT binary patch
literal 0
Hc$@<O00001

deleted file mode 100644
index 2a6b04241cb3920098af122a413107d9ebab4a4e..0000000000000000000000000000000000000000
GIT binary patch
literal 0
Hc$@<O00001

--- a/mail/themes/shared/mail/tabmail.css
+++ b/mail/themes/shared/mail/tabmail.css
@@ -9,25 +9,20 @@
   --tabCurveWidth: 30px;
   --tabCurveWidthNegative: -30px;
   --tabCurveHalfWidth: 15px;
   --tabCurveHalfWidthNegative: -15px;
   --tabBackgroundImage: url("chrome://messenger/skin/tabs/background-start.png"),
                         url("chrome://messenger/skin/tabs/background-middle.png"),
                         url("chrome://messenger/skin/tabs/background-end.png");
   --tab-stroke-background-size: auto 100%;
-  --tab-separator-image: url(chrome://messenger/skin/tabs/separator.png);
-  --tab-separator-size: 3px 100%;
-  --tab-separator-opacity: 1;
+  --tab-separator-opacity: 0.2;
 }
 
 #tabs-toolbar[brighttext] {
-  --tab-separator-image: linear-gradient(transparent 0%, transparent 15%,
-                         currentColor 15%, currentColor 90%, transparent 90%);
-  --tab-separator-size: 1px 100%;
   --tab-separator-opacity: 0.4;
 }
 
 /* image preloading hack */
 #tabs-toolbar::before {
   /* Because of bug 853415, we need to ordinal this to the first position: */
   -moz-box-ordinal-group: 0;
   content: '';
@@ -222,30 +217,33 @@
   pointer-events: none;
 }
 
 .tab-background-middle,
 .tab-close-button {
   pointer-events: auto;
 }
 
-/* Background tab separators (3px wide). */
+/* Tab separators */
+.tabmail-tab::before {
+  width: 1px;
+  margin-inline-start: -1px;
+  background-image: linear-gradient(transparent 5px,
+                                    currentColor 5px,
+                                    currentColor calc(100% - 4px),
+                                    transparent calc(100% - 4px));
+  opacity: 0;
+  content: '';
+  display: -moz-box;
+}
+
 .tabmail-tab:not([selected]):not(:hover) +
 .tabmail-tab:not([selected]):not(:hover)::before {
-  -moz-margin-start: -1.5px;
-  -moz-margin-end: -1.5px;
-  background-image: var(--tab-separator-image);
-  background-position: left bottom;
-  background-repeat: no-repeat;
-  background-size: var(--tab-separator-size);
   opacity: var(--tab-separator-opacity);
-  content: '';
-  display: -moz-box;
-  margin-bottom: 1px;
-  width: 3px;
+  transition: opacity 100ms ease;
 }
 
 /* Tab Overflow */
 .tabmail-arrowscrollbox > .arrowscrollbox-overflow-start-indicator:not([collapsed]),
 .tabmail-arrowscrollbox > .arrowscrollbox-overflow-end-indicator:not([collapsed]) {
   background-image: url("chrome://messenger/skin/tabs/overflow-indicator.png");
   background-size: 100% 100%;
   width: 14px;

--- a/mail/themes/windows/jar.mn
+++ b/mail/themes/windows/jar.mn
@@ -272,18 +272,16 @@ classic.jar:
   skin/classic/messenger/tabs/background-middle-win10@2x.png  (mail/tabs/background-middle-win10@2x.png)
   skin/classic/messenger/tabs/background-start.png            (mail/tabs/background-start.png)
   skin/classic/messenger/tabs/background-start-win10.png      (mail/tabs/background-start-win10.png)
   skin/classic/messenger/tabs/background-start@2x.png         (mail/tabs/background-start@2x.png)
   skin/classic/messenger/tabs/background-start-win10@2x.png   (mail/tabs/background-start-win10@2x.png)
   skin/classic/messenger/tabs/overflow-indicator.png          (mail/tabs/overflow-indicator.png)
   skin/classic/messenger/tabs/selected-end.svg                (mail/tabs/selected-end.svg)
   skin/classic/messenger/tabs/selected-start.svg              (mail/tabs/selected-start.svg)
-  skin/classic/messenger/tabs/separator.png                   (mail/tabs/separator.png)
-  skin/classic/messenger/tabs/separator-XP.png                (mail/tabs/separator-XP.png)
   skin/classic/messenger/tabs/stroke-end.png                  (mail/tabs/stroke-end.png)
   skin/classic/messenger/tabs/stroke-end@2x.png               (mail/tabs/stroke-end@2x.png)
   skin/classic/messenger/tabs/stroke-start.png                (mail/tabs/stroke-start.png)
   skin/classic/messenger/tabs/stroke-start@2x.png             (mail/tabs/stroke-start@2x.png)
   skin/classic/messenger/icons/connecting.png                 (mail/icons/connecting.png)
   skin/classic/messenger/icons/loading.png                    (mail/icons/loading.png)
   skin/classic/messenger/icons/notloading.png                 (mail/icons/notloading.png)
   skin/classic/messenger/icons/chat-toolbar.png               (mail/icons/chat-toolbar.png)

--- a/mail/themes/windows/mail/tabmail.css
+++ b/mail/themes/windows/mail/tabmail.css
@@ -109,21 +109,16 @@
     background-color: rgba(255,255,255,.5);
   }
 
   .tabmail-tabs:-moz-lwtheme {
     padding-top: 1px;
     background-color: transparent;
     background-image: none;
   }
-
-  .tabmail-tab:not([selected]):not(:hover) +
-  .tabmail-tab:not([selected]):not(:hover)::before {
-    background-image: url("chrome://messenger/skin/tabs/separator-XP.png");
-  }
 }
 
 @media (-moz-os-version: windows-win10) {
   #tabs-toolbar {
     --tabBackgroundImage: url(chrome://messenger/skin/tabs/background-start-win10.png),
                           url(chrome://messenger/skin/tabs/background-middle-win10.png),
                           url(chrome://messenger/skin/tabs/background-end-win10.png);
     --tab-stroke-background-size: 0 0;
@@ -388,23 +383,16 @@ tabpanels {
 
   .tabs-alltabs-button > .toolbarbutton-menu-dropmarker {
     display: none;
   }
 }
 
 @media (-moz-os-version: windows-win8),
        (-moz-os-version: windows-win10) {
-  #tabs-toolbar:not([brighttext]) {
-    --tab-separator-image: linear-gradient(transparent 0%, transparent 15%,
-                           currentColor 15%, currentColor 90%, transparent 90%);
-    --tab-separator-size: 1px 100%;
-    --tab-separator-opacity: 0.2;
-  }
-
   .tabs-alltabs-button {
     list-style-image: url(icons/dropmarker.svg#win8);
   }
 
   #tabs-toolbar[brighttext] .tabs-alltabs-button {
     list-style-image: url(icons/dropmarker.svg#win8-inverted);
   }
 

deleted file mode 100644
index 67af32ee9ffca4ab8322833d2b02995cf70ba6d5..0000000000000000000000000000000000000000
GIT binary patch
literal 0
Hc$@<O00001

deleted file mode 100644
index 8f46ed201249696e03e6ebd408afca7faa2ec237..0000000000000000000000000000000000000000
GIT binary patch
literal 0
Hc$@<O00001