--- a/mail/installer/Makefile.in
+++ b/mail/installer/Makefile.in
@@ -165,16 +165,20 @@ endif
 
 ifdef CLANG_CXX
 DEFINES += -DCLANG_CXX
 endif
 ifdef CLANG_CL
 DEFINES += -DCLANG_CL
 endif
 
+ifdef TB_LIBOTR_PREBUILT
+DEFINES += -DTB_LIBOTR_PREBUILT
+endif
+
 libs::
 	$(MAKE) -C $(commtopobjdir)/mail/locales langpack
 
 ifeq (WINNT,$(OS_ARCH))
 PKGCOMP_FIND_OPTS =
 else
 PKGCOMP_FIND_OPTS = -L
 endif

--- a/mail/installer/package-manifest.in
+++ b/mail/installer/package-manifest.in
@@ -216,16 +216,34 @@
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 @RESPATH@/@PREF_DIR@/chat-prefs.js
 @RESPATH@/chrome/chat@JAREXT@
 @RESPATH@/chrome/chat.manifest
 
 ; Thunderbird specific
 @RESPATH@/@PREF_DIR@/all-im.js
 
+; OTR libraries
+#ifdef TB_LIBOTR_PREBUILT
+#ifdef XP_WIN
+@BINPATH@/libotr-5.dll
+@BINPATH@/libgcrypt-20.dll
+@BINPATH@/libssp-0.dll
+#ifdef _AMD64_
+@BINPATH@/libgpg-error6-0.dll
+#else
+@BINPATH@/libgpg-error-0.dll
+#endif
+#elif defined(XP_MACOSX)
+@BINPATH@/libotr.5.dylib
+#elif defined(XP_LINUX)
+@BINPATH@/libotr.so.5
+#endif
+#endif
+
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 ; Chrome Files
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 
 @RESPATH@/chrome/classic@JAREXT@
 @RESPATH@/chrome/classic.manifest
 
 ; [DevTools Startup Files]

--- a/mail/moz.build
+++ b/mail/moz.build
@@ -16,15 +16,17 @@ DIRS += [
 ]
 
 if CONFIG['MAKENSISU']:
     DIRS += ['installer/windows']
 
 if CONFIG['MOZ_BUNDLED_FONTS']:
     DIRS += ['/%s/browser/fonts' % CONFIG['mozreltopsrcdir']]
 
+DIRS += ['../third_party']
+
 TEST_DIRS += [
     'test/browser',
     'test/marionette',
     'test/static',
 ]
 
 FINAL_TARGET_FILES.defaults += ['app/permissions']

--- a/mail/moz.configure
+++ b/mail/moz.configure
@@ -75,16 +75,32 @@ imply_option('MOZ_BLOCK_PROFILE_DOWNGRAD
 
 with only_when(target_is_linux & compile_environment):
     option(env='MOZ_NO_PIE_COMPAT',
            help='Enable non-PIE wrapper')
 
     set_config('MOZ_NO_PIE_COMPAT',
                depends_if('MOZ_NO_PIE_COMPAT')(lambda _: True))
 
+
+@depends('MOZ_AUTOMATION')
+@imports(_from='os', _import='environ')
+@imports(_from='six', _import='ensure_text')
+def pkg_libotr(automation):
+    if automation:
+        fetch_dir = environ.get('MOZ_FETCHES_DIR', None)
+        if fetch_dir:
+            log.info('Including libotr from {}'.format(fetch_dir))
+            return ensure_text(fetch_dir)
+
+        log.info('TB_LIBOTR_PREBUILT is set, but MOZ_FETCHES_DIR is invalid.')
+
+set_config('TB_LIBOTR_PREBUILT', pkg_libotr)
+
+
 set_config('MOZ_TELEMETRY_EXTRA_HISTOGRAM_FILES', ['/comm/mail/components/telemetry/Histograms.json'])
 set_config('MOZ_TELEMETRY_EXTRA_SCALAR_FILES', ['/comm/mail/components/telemetry/Scalars.yaml'])
 set_config('MOZ_TELEMETRY_EXTRA_EVENT_FILES', ['/comm/mail/components/telemetry/Events.yaml'])
 
 include('../build/moz.configure/gecko_source.configure')
 
 include('../mailnews/moz.configure')
 

new file mode 100644
--- /dev/null
+++ b/third_party/Makefile.in
@@ -0,0 +1,38 @@
+# 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/.
+
+
+include $(moztopsrcdir)/config/config.mk
+include $(moztopsrcdir)/config/rules.mk
+
+print-%: ; @echo $* is $($*)
+origin-%: ; @echo $* origin $(origin $*)
+
+ifdef TB_LIBOTR_PREBUILT
+
+ifeq (WINNT,$(OS_ARCH))
+ifdef HAVE_64BIT_BUILD
+OTR_LIBS := libgpg-error6-0.dll
+else
+OTR_LIBS := libgpg-error-0.dll
+endif
+OTR_LIBS += libgcrypt-20.dll \
+	libotr-5.dll \
+	libssp-0.dll
+endif
+
+ifeq (Darwin,$(OS_ARCH))
+OTR_LIBS := libotr.5.dylib
+endif
+
+ifeq (Linux,$(OS_ARCH))
+OTR_LIBS := libotr.so.5
+endif
+
+OTR_LIB_PATHS := $(foreach otrlib,$(OTR_LIBS),$(TB_LIBOTR_PREBUILT)/$(otrlib))
+
+libs:: $(OTR_LIB_PATHS)
+	$(NSINSTALL) -t -m 755 $(OTR_LIB_PATHS) $(DIST)/bin
+
+endif   ## TB_LIBOTR_PREBUILT

new file mode 100644
--- /dev/null
+++ b/third_party/moz.build
@@ -0,0 +1,10 @@
+# vim: set filetype=python:
+# 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/.
+
+if CONFIG['TB_LIBOTR_PREBUILT']:
+    DEFINES['TB_LIBOTR_PREBUILT'] = CONFIG['TB_LIBOTR_PREBUILT']
+
+    if CONFIG['HAVE_64BIT_BUILD']:
+        DEFINES['HAVE_64BIT_BUILD'] = True