--- a/mail/app/thunderbird.exe.manifest
+++ b/mail/app/thunderbird.exe.manifest
@@ -23,17 +23,17 @@
   <ms_asmv3:security>
     <ms_asmv3:requestedPrivileges>
       <ms_asmv3:requestedExecutionLevel level="asInvoker" uiAccess="false" />
     </ms_asmv3:requestedPrivileges>
   </ms_asmv3:security>
 </ms_asmv3:trustInfo>
   <ms_asmv3:application xmlns:ms_asmv3="urn:schemas-microsoft-com:asm.v3">
     <ms_asmv3:windowsSettings xmlns="http://schemas.microsoft.com/SMI/2005/WindowsSettings">
-      <dpiAware>true</dpiAware>
+      <dpiAware>True/PM</dpiAware>
     </ms_asmv3:windowsSettings>
   </ms_asmv3:application>
   <compatibility xmlns="urn:schemas-microsoft-com:compatibility.v1">
     <application>
       <supportedOS Id="{8e0f7a12-bfb3-4fe8-b9a5-48fd50a15a9a}"/>
       <supportedOS Id="{1f676c76-80e1-4239-95bb-83d0f6d0da78}"/>
       <supportedOS Id="{4a2f28e3-53b9-4441-ba9c-d69d4a4a6e38}"/>
       <supportedOS Id="{35138b9a-5d96-4fbd-8e2d-a2440225f93a}"/>

--- a/mail/base/content/aboutDialog.css
+++ b/mail/base/content/aboutDialog.css
@@ -1,14 +1,18 @@
 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 #aboutDialog {
   width: 620px;
+  /* Set an explicit line-height to avoid discrepancies in 'auto' spacing
+     across screens with different device DPI, which may cause font metrics
+     to round differently. */
+  line-height: 1.5;
 }
 
 #rightBox {
   background-image: url("chrome://branding/content/about-wordmark.png");
   background-repeat: no-repeat;
   /* padding-top creates room for the wordmark */
   padding-top: 38px;
   margin-top:20px;