Bug 1911916 - Part 5 of 6. Preserve mbox "From "-line sender/timestamp during compaction. r=tobyp

Differential Revision: https://phabricator.services.mozilla.com/D222062

--HG--
extra : moz-landing-system : lando

mailnews/local/src/nsMsgBrkMBoxStore.cpp

@@ -374,6 +374,8 @@ NS_IMETHODIMP MboxCompactor::OnStartMessage(nsACString const& storeToken,
     MOZ_ASSERT(mDestStream);
     MOZ_ASSERT(!mMsgOut);
     mMsgOut = new MboxMsgOutputStream(mDestStream, false);
+    // Preserve metadata on the "From " line.
+    mMsgOut->SetEnvelopeDetails(envAddr, envDate);
   }
 
   return NS_OK;