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Poloniex should be working again now. However Bittrex is the better exchange to use, they rarely have any issues.

As noted below, Bittrex isn't accepting new users, so use @blocktrades instead.

Bittrex is not taking new clients for now, however. Poloniex is working again but they are always a risk of having issues.

I wasn't aware of that. @blocktrades is your friend in that case.

Frightening thought. We need some more alt-coin exchanges to step up and take on STEEM trading. I have high hopes for Binance.

Ok, now I see. Thanks a lot ! I will try it.