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What you're observing seems to be perfectly normal with Cox's "improvement".  Email speeds vary- from barely acceptable at best to paralyzingly slow and connection errors.  Complaining too much may prompt well-meaning forum moderators to dispatch you on cache and cookies clearing missions that will most likely have a negligible effect on webmail speeds.  I tend to have an easier time late at night when web traffic is down.  I experience connection errors on a very regular basis and am resigned to accepting them as normal.