I looked at the CEX.IO website and couldn't find any doge or namecoin markets. Are you sure it was CEX.IO that sent the email? The only CEX.IO markets I could find were for bitcoin, ethereum, and litecoin, but I have never registered on it so I might have missed some.
Yes it was from them. There was a time when I mined on ghash.io (owned by cex.io) and you could sell merged mined coins like doge and namecoin directly on the exchange. Haven't visited in years; but, still receive emails.
Thanks, I checked on the internet archive and found historical webpage snapshots showing the old dogecoin and namecoin markets.
The stats for ghash.io at btc.com say it didn't mine a block in November, and only got four in October. There's a chart showing it was a massive pool in 2014, but has tailed off to insignificant now. Ghash/cex.io could be getting so desparate for money that it's raiding members old wallets.
https://btc.com/stats/pool/GHash.IO