he/him 
The @WellsFargo bill pay function is such a massive arbitrage scam.
It literally sends a paper cheque in physical mail taking 5 business days or more, but the amount is taken from the account immediately.
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I believe they're just writing a cashier's check which is a guarantee of funds. To make the guarantee, money has to come out immediately. Has to be check, since most bill payments systems are stuck in decades old system.
I'm with Charles Schwab and use their bill pay feature where they send a physical check. Money only comes out when it's deposited. Wells Fargo don't have to do this.