Fidelity International also launched environmental, social and governance ETFs this week.
The letter comes from 109 investors, representing €11.9 trillion in assets under management or advice.
Business has grown since March as clients want ‘anytime, anywhere’ access to a virtual trading floor.
The regulator said market participants should not become overly reliant on their cloud services providers.
"Robots will learn an awful lot" from March's extreme volatility.
The industry spends more than $20bn a year processing trades.
UK-based Caspian is an industry leader in automated AML investigation technology.
There are closures across Chicago and limited access to the area surrounding the Cboe building.
Investors can seek liquidity following the closing auction via a dark undisclosed execution channel.