You've Got Mail (1998) on Netflix

Kathleen Kelly, owner of a little and famous bookstore for children's books, has an affair. Being together with Frank Navasky, a well-known journalist, she betrays him by e-mailing secretly and anonymously with a (also betraying) man whom she met in a chat room. Suddenly, her business gets endangered by the opening of Fox Books discount store just "around the corner". She meets Joe Fox, son of the owner, and soon gets annoyed by his arrogant way of managing business matters. Although getting advice by her anonymous mail-pal, she has to close down her store. But Joe Fox's life suddenly gets out of control when he learns that his anonymous mail-pal is nobody other than Kathleen Kelly.