fix handling of online sub directories with imap namespaces, r/sr=mscott 219645

mailnews/imap/src/nsImapUrl.cpp

@@ -861,6 +861,10 @@ NS_IMETHODIMP nsImapUrl::AddOnlineDirectoryIfNecessary(const char *onlineMailbox
         }
       }
       if (ns && (PL_strlen(ns->GetPrefix()) != 0) && !onlineDirWithDelimiter.Equals(ns->GetPrefix()))
+      {
+        // check that onlineMailboxName doesn't start with the namespace. If that's the case,
+        // we don't want to prepend the online dir.
+        if (PL_strncmp(onlineMailboxName, ns->GetPrefix(), PL_strlen(ns->GetPrefix())))
         {
           // The namespace for this mailbox is the root ("").
           // Prepend the online server directory
@@ -873,6 +877,7 @@ NS_IMETHODIMP nsImapUrl::AddOnlineDirectoryIfNecessary(const char *onlineMailbox
             PL_strcat(newOnlineName, onlineMailboxName);
           }
         }
+      }
       // just prepend the online server directory if it doesn't start with it already
       else if (strncmp(onlineMailboxName, onlineDirWithDelimiter.get(), onlineDirWithDelimiter.Length()))
       {