Is wrong to steal clients from your employer
John is an accountant leaving his employer of several years to start his own business.
John wants to start his new business off with lots of clients.
John advertises heavily prior to opening his business, and gets many new clients when he opens.
John copies the e-mails of several top clients at his old job and reaches out to them with lower rates than his old employer which they accept.
John's business thrives while earning reasonable rates from his new customers.
John's old employer finds out about this, and responds in kind with an insuing pricing war.