Tux Exchange is currently not operating. It was closed in 2019 with a prior announcement as of June 15, 2019. July 6, 2019, was the deadline for the withdrawal of funds. Tux Exchange referred to “unfavorable conditions” and “low volume” as key factors stipulating the decision to close down.

QuadrigaCX is a Centralized cryptocurrency exchange based in the Canada. The exchange was launched in 2013. Its reported volume is about 0 $ as for 8 October 2019.
QuadrigaCX has 0 available trading pairs and 0 coins. Deposits are Depends on currency and volume on the exchange.
QuadrigaCX have Fiat...

In March, 2020 GuldenTrader exchange has published an announcement calling its customers to withdraw their funds before April 1, when the exchange will cease its operation.

It became known in spring 2019 that Gatecoin exchange would stop its operation. It was stipulated by the decision of the Hong Kong court after quite a long attempt to recover lost funds. The loss amounted to $2 mln.

Chinese platform FCoin announced in February, 2020 that the exchange will stop its operation. A founder of the exchange explained this decision by internal errors.  FCoin still owes its users the amount from 7.000 to 13.000 BTC. 

DOBI is a digital asset trading platform. Apart from the English version, the website has also Chinese and Portugese versions. 

Dex.top is a decentralized cryptocurrency trading platform offering trading with smart contracts (including but not limited to Ethereum, EOS and NEO). The platform describes itself as World’s First Multi-Chain Decentralized Exchange and claims to have top volume among other decentralized exchanges. 

Cryptopia exchange was closed after a theft that took place in early 2019. Cryptopia was established in New Zealand in 2014. Its website had been publishing updates on the liquidation process until the mid-2019. 

Cryptonex is a centralized cryptocurrency exchange launched in 2017. Its reported volume is about 250007314 $ as of 8 October 2019. Cryptonex has 18 available trading pairs and 8 coins. Deposits are free on the exchange. Cryptonex has fiat deposits option. Margin trading option is not available on the exchange. Cryptonex is quite active in social media, with more than 25000 Twitter followers. You can leave your review about Cryptonex here.

CRXzone is the brand name for crypto exchange and merchant payment gateway. Trading pairs available with CRXzone include fiat currencies: USD (US dollar) and SGD (Singapore dollar). The exchange aims to provide deep liquidity.

CredoEx was introduced to the market by BitBounce in 2018. At the moment, the company’s website is down and Twitter media has not been updated since mid-2019

CPDAX was established in 2017 and stands for the “Coinplug Digital Asset Exchange”. It accepts KRW (Korean Won) deposit and withdrawal. This exchange is the development of the Coinplug blockchain technology company.

CoinZest exchange was founded in South Korea in 2018, maintaining deposit and withdrawal of fiat currency, Korean Won. At the point, the company’s website is down and Twitter media has not been updated since October, 2019.

CoinTiger is incorporated under the laws of the Republic of Singapore and works as a centralized exchange. It offers BTC, ETH, USDT, TRX, XRP markets, as well as trading pairs against bitCNY token.

In 2019, Coinroom has filed an application for bankruptcy with the last notice on their website published as of September 30. It was reported that this Polish exchange disappeared with customers’ funds.

Coinrate is currently inactive. The exchange’s website does not display any active orders in the trading window. The social media channels of the company had not been updated for about 2 years. Initially, Coinrate offered fiat currencies as well as Bitcoin and Fargocoin as the main currencies in trading pairs.

Coinnest was closed in June 2019 as per the announcement made in advance so that customers could withdraw their assets. There is information that the exchange has made errors in airdrops before.

Update: It seems like the CoinMex exchange shut down, possibly exit scammed.
CoinMex provides access to BTC, ETH, USDT and NEO markets. The company was incorporated under the legislation of the Republic of Seychelles in 2018 and is affiliated with NEWEX Technology Co. Ltd. CoinMex is focused on the Chinese market. 

Coinmama is a platform providing users with an opportunity to quickly buy cryptocurrencies with a credit card, Apple Pay, or via wire transfer. The registration doesn't take much time and the interface is quite intuitive. Coinmama isn't suited well for regular trading as the fees on the platform are quite high. So basically, Coinmama is good for buying cryptocurrencies for the first time. In this article, we will answer the most vital questions concerning the use of the service: is it safe to use Coinmama? Is Coinmama a scam? What are the fees on the platform? What are the main features of the platform? What is needed to sign up for Coinmama? And others...

The exchange was closed in 2019 with the preliminary notice informing about suspension of trading and deposit. Withdrawals had been operational for a couple of months since that time till December 1, 2019. The team explained the termination of activity by business reasons.