--- a/mailnews/base/util/nsMsgProtocol.cpp
+++ b/mailnews/base/util/nsMsgProtocol.cpp
@@ -467,19 +467,19 @@ nsresult nsMsgProtocol::LoadUrl(nsIURI *
         {
           // open buffered, asynchronous input stream
           rv = m_transport->OpenInputStream(0, 0, 0, getter_AddRefs(m_inputStream));
           if (NS_FAILED(rv)) return rv;
         }
 
         int64_t offset = 0;
         nsCOMPtr<nsISeekableStream> seekable(do_QueryInterface(m_inputStream));
-        if (seekable)
-          seekable->Tell(&offset);
-
+        if (seekable && NS_FAILED(seekable->Tell(&offset))) {
+          offset = 0;
+        }
         // m_readCount can be -1 which means "read as much as we can".
         // We pass this on as UINT64_MAX, which is in fact uint64_t(-1).
         RefPtr<SlicedInputStream> slicedStream =
           new SlicedInputStream(m_inputStream, uint64_t(offset),
                                 m_readCount == -1 ? UINT64_MAX : uint64_t(m_readCount));
         nsCOMPtr<nsIInputStreamPump> pump;
         rv = NS_NewInputStreamPump(getter_AddRefs(pump), slicedStream);
         if (NS_FAILED(rv)) return rv;