new file mode 100644
--- /dev/null
+++ b/build/win32/check-sync-exceptions
@@ -0,0 +1,2 @@
+# We can't use VS 2017 on buildbot.
+mozconfig.vs-latest

--- a/build/win32/mozconfig.vs-latest
+++ b/build/win32/mozconfig.vs-latest
@@ -1,1 +1,5 @@
-. $topsrcdir/build/win32/mozconfig.vs2017
+if [ "$MOZ_IS_COMM_TOPDIR" == "1" ]; then
+  . $topsrcdir/build/win32/mozconfig.vs2015-win64
+else
+  . $topsrcdir/build/win32/mozconfig.vs2017
+fi

--- a/mail/config/mozconfigs/win32/debug
+++ b/mail/config/mozconfigs/win32/debug
@@ -1,8 +1,9 @@
+. "$topsrcdir/build/mozconfig.comm-support"
 . "$topsrcdir/build/mozconfig.win-common"
 . "$topsrcdir/build/mozconfig.common"
 . "$topsrcdir/build/mozconfig.stylo"
 
 ac_add_options --enable-application=mail
 ac_add_options --enable-debug
 ac_add_options --enable-calendar
 

--- a/mail/config/mozconfigs/win32/l10n-mozconfig
+++ b/mail/config/mozconfigs/win32/l10n-mozconfig
@@ -1,8 +1,9 @@
+. "$topsrcdir/build/mozconfig.comm-support"
 . "$topsrcdir/build/mozconfig.common"
 . "$topsrcdir/build/mozconfig.stylo"
 
 ac_add_options --enable-application=mail
 ac_add_options --enable-update-channel=${MOZ_UPDATE_CHANNEL}
 ac_add_options --with-l10n-base=../../l10n
 # The compile environment is needed for Windows, see bug 1345422 comment #58.
 # ac_add_options --disable-compile-environment

--- a/mail/config/mozconfigs/win32/nightly
+++ b/mail/config/mozconfigs/win32/nightly
@@ -1,8 +1,9 @@
+. "$topsrcdir/build/mozconfig.comm-support"
 . "$topsrcdir/build/mozconfig.win-common"
 . "$topsrcdir/build/mozconfig.common"
 . "$topsrcdir/build/mozconfig.stylo"
 
 ac_add_options --enable-application=mail
 ac_add_options --enable-update-channel=${MOZ_UPDATE_CHANNEL}
 ac_add_options --enable-jemalloc
 ac_add_options --enable-profiling

--- a/mail/config/mozconfigs/win32/release
+++ b/mail/config/mozconfigs/win32/release
@@ -1,8 +1,9 @@
+. "$topsrcdir/build/mozconfig.comm-support"
 . "$topsrcdir/build/mozconfig.win-common"
 . "$topsrcdir/build/mozconfig.common"
 . "$topsrcdir/build/mozconfig.stylo"
 
 ac_add_options --enable-application=mail
 ac_add_options --enable-update-channel=${MOZ_UPDATE_CHANNEL}
 ac_add_options --enable-jemalloc
 ac_add_options --enable-official-branding

--- a/mail/config/tooltool-manifests/win32/releng.manifest
+++ b/mail/config/tooltool-manifests/win32/releng.manifest
@@ -9,16 +9,24 @@
     "version": "rustc 1.21.0 (3b72af97e 2017-10-09) repack",
     "size": 98327461,
     "digest": "f89ec6f274ccf91ab944ab4044f33ab0d3f8eaaca6fba090a69362f88aafcaf121eb03b3c089600c552fd8b9480ca92436b53231477b4a4080668d1f8558850b",
     "algorithm": "sha512",
     "filename": "rustc.tar.bz2",
     "unpack": true
   },
   {
+    "version": "Visual Studio 2015 Update 3 14.0.25425.01 / SDK 10.0.14393.0",
+    "size": 326656969,
+    "digest": "babc414ffc0457d27f5a1ed24a8e4873afbe2f1c1a4075469a27c005e1babc3b2a788f643f825efedff95b79686664c67ec4340ed535487168a3482e68559bc7",
+    "algorithm": "sha512",
+    "filename": "vs2015u3.zip",
+    "unpack": true
+  },
+  {
     "version": "Visual Studio 2017 15.4.1 / SDK 10.0.16299.0",
     "digest": "b22783f94d8c1304f9640e0cf0c614175c3f2e21f084bb08a31d5b3dc2f387e38a6917170eeb37e6446f191f2d685ca69c5e935f9d18ef41d16abf3a3b981d63",
     "size": 322544627,
     "algorithm": "sha512",
     "filename": "vs2017_15.4.1.zip",
     "unpack": true
   },
   {

--- a/suite/config/mozconfigs/win32/debug
+++ b/suite/config/mozconfigs/win32/debug
@@ -1,8 +1,9 @@
+. "$topsrcdir/build/mozconfig.comm-support"
 . "$topsrcdir/build/mozconfig.win-common"
 . "$topsrcdir/build/mozconfig.common"
 . "$topsrcdir/build/mozconfig.stylo"
 . "$topsrcdir/build/win32/mozconfig.vs-latest"
 . "$topsrcdir/suite/config/mozconfigs/common"
 
 ac_add_options --enable-application=suite
 ac_add_options --enable-debug

--- a/suite/config/mozconfigs/win32/l10n-mozconfig
+++ b/suite/config/mozconfigs/win32/l10n-mozconfig
@@ -1,8 +1,9 @@
+. "$topsrcdir/build/mozconfig.comm-support"
 . "$topsrcdir/build/mozconfig.win-common"
 . "$topsrcdir/build/mozconfig.common"
 . "$topsrcdir/build/mozconfig.stylo"
 . "$topsrcdir/build/win32/mozconfig.vs-latest"
 . "$topsrcdir/suite/config/mozconfigs/common"
 
 ac_add_options --with-l10n-base=../../l10n
 ac_add_options --enable-application=suite

--- a/suite/config/mozconfigs/win32/nightly
+++ b/suite/config/mozconfigs/win32/nightly
@@ -1,8 +1,9 @@
+. "$topsrcdir/build/mozconfig.comm-support"
 . "$topsrcdir/build/mozconfig.win-common"
 . "$topsrcdir/build/mozconfig.common"
 . "$topsrcdir/build/mozconfig.stylo"
 . "$topsrcdir/build/win32/mozconfig.vs-latest"
 . "$topsrcdir/suite/config/mozconfigs/mozconfig.win.common"
 . "$topsrcdir/suite/config/mozconfigs/common"
 
 ac_add_options --enable-application=suite

--- a/suite/config/mozconfigs/win32/release
+++ b/suite/config/mozconfigs/win32/release
@@ -1,8 +1,9 @@
+. "$topsrcdir/build/mozconfig.comm-support"
 . "$topsrcdir/build/mozconfig.win-common"
 . "$topsrcdir/build/mozconfig.common"
 . "$topsrcdir/build/mozconfig.stylo"
 . "$topsrcdir/build/win32/mozconfig.vs-latest"
 . "$topsrcdir/suite/config/mozconfigs/mozconfig.win.common"
 . "$topsrcdir/suite/config/mozconfigs/common"
 
 ac_add_options --enable-application=suite

--- a/suite/config/mozconfigs/win32/release-l10n
+++ b/suite/config/mozconfigs/win32/release-l10n
@@ -1,8 +1,9 @@
+. "$topsrcdir/build/mozconfig.comm-support"
 . "$topsrcdir/build/mozconfig.win-common"
 . "$topsrcdir/build/mozconfig.common"
 . "$topsrcdir/build/mozconfig.stylo"
 . "$topsrcdir/build/win32/mozconfig.vs-latest"
 . "$topsrcdir/suite/config/mozconfigs/common"
 
 ac_add_options --with-l10n-base=../../l10n
 ac_add_options --enable-application=suite