--- a/mailnews/base/public/msgCore.h
+++ b/mailnews/base/public/msgCore.h
@@ -21,22 +21,24 @@ class nsIMsgFolder;
 #include "nsIServiceManager.h"
 #include "nsIComponentManager.h"
 
 /*
  * The suffix we use for the mail summary file.
  */
 #define SUMMARY_SUFFIX u".msf"
 #define SUMMARY_SUFFIX8 ".msf"
+#define SUMMARY_SUFFIX_LENGTH 4
 
 /*
  * The suffix we use for folder subdirectories.
  */
 #define FOLDER_SUFFIX u".sbd"
 #define FOLDER_SUFFIX8 ".sbd"
+#define FOLDER_SUFFIX_LENGTH 4
 
 /*
  * These are folder property strings, which are used in several places.
 
  */
 // Most recently used (opened, moved to, got new messages)
 #define MRU_TIME_PROPERTY "MRUTime"
 // Most recently moved to, for recent folders list in move menu

--- a/mailnews/base/search/src/nsMsgFilter.cpp
+++ b/mailnews/base/search/src/nsMsgFilter.cpp
@@ -791,21 +791,21 @@ nsresult nsMsgFilter::ConvertMoveOrCopyT
       }
       if (NS_SUCCEEDED(rv) && localMailRoot)
       {
         nsCString localRootURI;
         nsCOMPtr <nsIMsgFolder> destIMsgFolder;
         nsCOMPtr <nsIMsgFolder> localMailRootMsgFolder = do_QueryInterface(localMailRoot);
         localMailRoot->GetURI(localRootURI);
         nsCString destFolderUri;
-        destFolderUri.Assign( localRootURI);
+        destFolderUri.Assign(localRootURI);
         // need to remove ".sbd" from moveValue, and perhaps escape it.
-        int32_t offset = moveValue.Find(".sbd/");
+        int32_t offset = moveValue.Find(FOLDER_SUFFIX8 "/");
         if (offset != -1)
-          moveValue.Cut(offset, 4);
+          moveValue.Cut(offset, FOLDER_SUFFIX_LENGTH);
 
 #ifdef XP_MACOSX
         nsCString unescapedMoveValue;
         MsgUnescapeString(moveValue, 0, unescapedMoveValue);
         moveValue = unescapedMoveValue;
 #endif
         destFolderUri.Append('/');
         if (filterVersion == k45Version)

--- a/mailnews/base/util/nsMsgDBFolder.cpp
+++ b/mailnews/base/util/nsMsgDBFolder.cpp
@@ -918,17 +918,17 @@ nsresult nsMsgDBFolder::CreateFileForDB(
   dbPath->Exists(&exists);
   if (exists)
   {
     rv = dbPath->CreateUnique(nsIFile::NORMAL_FILE_TYPE, 00600);
     NS_ENSURE_SUCCESS(rv, rv);
     dbPath->GetLeafName(proposedDBName);
   }
   // now, take the ".msf" off
-  proposedDBName.SetLength(proposedDBName.Length() - NS_LITERAL_STRING(SUMMARY_SUFFIX).Length());
+  proposedDBName.SetLength(proposedDBName.Length() - SUMMARY_SUFFIX_LENGTH);
   dbPath->SetLeafName(proposedDBName);
 
   dbPath.forget(dbFile);
   return NS_OK;
 }
 
 NS_IMETHODIMP
 nsMsgDBFolder::GetMsgDatabase(nsIMsgDatabase** aMsgDatabase)
@@ -4067,17 +4067,17 @@ NS_IMETHODIMP nsMsgDBFolder::Rename(cons
   {
     ThrowAlertMsg("folderRenameFailed", msgWindow);
     return rv;
   }
 
   if (NS_SUCCEEDED(rv) && count > 0)
   {
     // rename "*.sbd" directory
-    newNameDirStr.AppendLiteral(".sbd");
+    newNameDirStr.AppendLiteral(FOLDER_SUFFIX);
     dirFile->MoveTo(nullptr, newNameDirStr);
   }
 
   nsCOMPtr<nsIMsgFolder> newFolder;
   if (parentSupport)
   {
     rv = parentFolder->AddSubfolder(aNewName, getter_AddRefs(newFolder));
     if (newFolder)

--- a/mailnews/base/util/nsMsgUtils.cpp
+++ b/mailnews/base/util/nsMsgUtils.cpp
@@ -577,17 +577,17 @@ nsresult NS_MsgCreatePathStringFromFolde
     pathPiece.Assign(Substring(oldPath, startSlashPos + 1, endSlashPos - startSlashPos));
     // skip leading '/' (and other // style things)
     if (!pathPiece.IsEmpty())
     {
 
       // add .sbd onto the previous path
       if (haveFirst)
       {
-        path.AppendLiteral(".sbd/");
+        path.AppendLiteral(FOLDER_SUFFIX "/");
       }
 
       if (aIsNewsFolder)
       {
           nsAutoCString tmp;
           CopyUTF16toMUTF7(pathPiece, tmp);
           CopyASCIItoUTF16(tmp, pathPiece);
       }

--- a/mailnews/db/msgdb/src/nsMailDatabase.cpp
+++ b/mailnews/db/msgdb/src/nsMailDatabase.cpp
@@ -40,17 +40,17 @@ nsMailDatabase::~nsMailDatabase()
 // If so, they'll extract out the interesting info from the db, close it, delete it, and
 // then try to open the db again, prior to reparsing.
 nsresult nsMailDatabase::Open(nsMsgDBService* aDBService, nsIFile *aSummaryFile,
                               bool aCreate, bool aUpgrading)
 {
 #ifdef DEBUG
   nsString leafName;
   aSummaryFile->GetLeafName(leafName);
-  if (!StringEndsWith(leafName, NS_LITERAL_STRING(".msf"),
+  if (!StringEndsWith(leafName, NS_LITERAL_STRING(SUMMARY_SUFFIX),
                      nsCaseInsensitiveStringComparator()))
     NS_ERROR("non summary file passed into open\n");
 #endif
   return nsMsgDatabase::Open(aDBService, aSummaryFile, aCreate, aUpgrading);
 }
 
 NS_IMETHODIMP nsMailDatabase::ForceClosed()
 {

--- a/mailnews/imap/src/nsImapMailFolder.cpp
+++ b/mailnews/imap/src/nsImapMailFolder.cpp
@@ -246,23 +246,19 @@ nsresult nsImapMailFolder::AddDirectoryS
   }
 
   return NS_OK;
 }
 
 static bool
 nsShouldIgnoreFile(nsString& name)
 {
-  int32_t len = name.Length();
-  // Warning: The first argument of RFind() needs to be a char string here so
-  // that the second argument means 'ignorecase'. When passing a char16_t here,
-  // a different overload is triggered and the argument is interpreted as offset.
-  if (len > 4 && name.RFind(SUMMARY_SUFFIX8, true) == len - 4)
-  {
-    name.SetLength(len-4); // truncate the string
+  if (StringEndsWith(name, NS_LITERAL_STRING(SUMMARY_SUFFIX), nsCaseInsensitiveStringComparator()))
+  {
+    name.SetLength(name.Length() - SUMMARY_SUFFIX_LENGTH); // truncate the string
     return false;
   }
   return true;
 }
 
 nsresult nsImapMailFolder::CreateChildFromURI(const nsCString &uri, nsIMsgFolder **folder)
 {
   nsImapMailFolder *newFolder = new nsImapMailFolder;
@@ -1709,17 +1705,17 @@ NS_IMETHODIMP nsImapMailFolder::RenameLo
   NS_ENSURE_SUCCESS(rv, rv);
 
   nsAutoCString newNameStr;
   oldSummaryFile->Remove(false);
   if (count > 0)
   {
     newNameStr = leafname;
     NS_MsgHashIfNecessary(newNameStr);
-    newNameStr += ".sbd";
+    newNameStr.AppendLiteral(FOLDER_SUFFIX8);
     nsAutoCString leafName;
     dirFile->GetNativeLeafName(leafName);
     if (!leafName.Equals(newNameStr))
       return dirFile->MoveToNative(nullptr, newNameStr);      // in case of rename operation leaf names will differ
 
     parentPathFile->AppendNative(newNameStr);    //only for move we need to progress further in case the parent differs
     bool isDirectory = false;
     parentPathFile->IsDirectory(&isDirectory);

--- a/mailnews/local/src/nsMsgBrkMBoxStore.cpp
+++ b/mailnews/local/src/nsMsgBrkMBoxStore.cpp
@@ -382,24 +382,24 @@ NS_IMETHODIMP nsMsgBrkMBoxStore::RenameF
 
   aFolder->ForceDBClosed();
   //save off dir name before appending .msf
   rv = oldPathFile->MoveTo(nullptr, safeName);
   if (NS_FAILED(rv))
     return rv;
 
   nsString dbName(safeName);
-  dbName += NS_LITERAL_STRING(SUMMARY_SUFFIX);
+  dbName.AppendLiteral(SUMMARY_SUFFIX);
   oldSummaryFile->MoveTo(nullptr, dbName);
 
   if (numChildren > 0)
   {
     // rename "*.sbd" directory
     nsAutoString newNameDirStr(safeName);
-    newNameDirStr += NS_LITERAL_STRING(".sbd");
+    newNameDirStr.AppendLiteral(FOLDER_SUFFIX);
     dirFile->MoveTo(nullptr, newNameDirStr);
   }
 
   return parentFolder->AddSubfolder(safeName, aNewFolder);
 }
 
 NS_IMETHODIMP nsMsgBrkMBoxStore::CopyFolder(nsIMsgFolder *aSrcFolder,
                                             nsIMsgFolder *aDstFolder,
@@ -457,17 +457,17 @@ NS_IMETHODIMP nsMsgBrkMBoxStore::CopyFol
   NS_ENSURE_SUCCESS(rv, rv); // Will fail if a file by that name exists
 
   // Copy to dir can fail if filespec does not exist. If copy fails, we test
   // if the filespec exist or not, if it does not that's ok, we continue
   // without copying it. If it fails and filespec exist and is not zero sized
   // there is real problem
   // Copy the file to the new dir
   nsAutoString dbName(safeFolderName);
-  dbName += NS_LITERAL_STRING(SUMMARY_SUFFIX);
+  dbName.AppendLiteral(SUMMARY_SUFFIX);
   rv = summaryFile->CopyTo(newPath, dbName);
   if (NS_FAILED(rv)) // Test if the copy is successful
   {
     // Test if the filespec has data
     bool exists;
     int64_t fileSize;
     summaryFile->Exists(&exists);
     summaryFile->GetFileSize(&fileSize);
@@ -1019,17 +1019,17 @@ nsMsgBrkMBoxStore::AddSubFolders(nsIMsgF
   path->IsDirectory(&isDirectory);
   if (!isDirectory)
   {
     rv = path->Clone(getter_AddRefs(tmp));
     path = tmp;
     NS_ENSURE_SUCCESS(rv, rv);
     nsAutoString leafName;
     path->GetLeafName(leafName);
-    leafName.AppendLiteral(".sbd");
+    leafName.AppendLiteral(FOLDER_SUFFIX);
     path->SetLeafName(leafName);
     path->IsDirectory(&isDirectory);
   }
   if (!isDirectory)
     return NS_OK;
   // first find out all the current subfolders and files, before using them
   // while creating new subfolders; we don't want to modify and iterate the same
   // directory at once.

--- a/mailnews/local/src/nsMsgLocalStoreUtils.cpp
+++ b/mailnews/local/src/nsMsgLocalStoreUtils.cpp
@@ -53,17 +53,17 @@ nsMsgLocalStoreUtils::nsShouldIgnoreFile
   // ignore RSS data source files
   if (name.LowerCaseEqualsLiteral("feeds.rdf") ||
       name.LowerCaseEqualsLiteral("feeditems.rdf") ||
       StringBeginsWith(name, NS_LITERAL_STRING("feeditems_error")))
     return true;
 
   // The .mozmsgs dir is for spotlight support
     return (StringEndsWith(name, NS_LITERAL_STRING(".mozmsgs")) ||
-            StringEndsWith(name, NS_LITERAL_STRING(".sbd")) ||
+            StringEndsWith(name, NS_LITERAL_STRING(FOLDER_SUFFIX)) ||
             StringEndsWith(name, NS_LITERAL_STRING(SUMMARY_SUFFIX)));
 }
 
 /**
  * We're passed a stream positioned at the start of the message.
  * We start reading lines, looking for x-mozilla-keys: headers; If we're
  * adding the keyword and we find a header with the desired keyword already
  * in it, we don't need to do anything. Likewise, if removing keyword and we

--- a/mailnews/local/src/nsMsgMaildirStore.cpp
+++ b/mailnews/local/src/nsMsgMaildirStore.cpp
@@ -376,23 +376,23 @@ NS_IMETHODIMP nsMsgMaildirStore::RenameF
   // rename folder
   rv = oldPathFile->MoveTo(nullptr, safeName);
   NS_ENSURE_SUCCESS(rv, rv);
 
   if (numChildren > 0)
   {
     // rename "*.sbd" directory
     nsAutoString sbdName = safeName;
-    sbdName += NS_LITERAL_STRING(FOLDER_SUFFIX);
+    sbdName.AppendLiteral(FOLDER_SUFFIX);
     sbdPathFile->MoveTo(nullptr, sbdName);
   }
 
   // rename summary
   nsAutoString summaryName(safeName);
-  summaryName += NS_LITERAL_STRING(SUMMARY_SUFFIX);
+  summaryName.AppendLiteral(SUMMARY_SUFFIX);
   oldSummaryFile->MoveTo(nullptr, summaryName);
 
   nsCOMPtr<nsIMsgFolder> parentFolder;
   rv = aFolder->GetParent(getter_AddRefs(parentFolder));
   if (!parentFolder)
     return NS_ERROR_NULL_POINTER;
 
   return parentFolder->AddSubfolder(safeName, aNewFolder);
@@ -442,17 +442,17 @@ NS_IMETHODIMP nsMsgMaildirStore::CopyFol
   rv = oldPath->CopyTo(newPath, safeFolderName);
   NS_ENSURE_SUCCESS(rv, rv); //will fail if a file by that name exists
 
   // Copy to dir can fail if file does not exist. If copy fails, we test
   // if the file exists or not, if it does not that's ok, we continue
   // without copying it. If it fails and file exist and is not zero sized
   // there is real problem.
   nsAutoString dbName(safeFolderName);
-  dbName += NS_LITERAL_STRING(SUMMARY_SUFFIX);
+  dbName.AppendLiteral(SUMMARY_SUFFIX);
   rv = summaryFile->CopyTo(newPath, dbName);
   if (!NS_SUCCEEDED(rv))
   {
     // Test if the file is not empty
     bool exists;
     int64_t fileSize;
     summaryFile->Exists(&exists);
     summaryFile->GetFileSize(&fileSize);