The CEO of a California startup apologized after an e-mail instructing his staff to tell an unhappy customer to "f--- off" ended up being sent to the client.

Customer Erin Boudreau of Seattle wasn't pleased with the service she received from Postmates — a delivery company based in San Francisco — so she e-mailed customer service.

But Boudreau was inadvertently sent an e-mail chain that included the nasty message from the company founder.

Bastian Lehmann, CEO of Postmates, said in a blog post the e-mail was sent in error to the woman and was a "bad joke which was very poor in taste."

Boudreau posted a photo of the offending message to Twitter.

Emailed @Postmates founder/CEO @basti to communicate my poor order history. He told me to "fuck off". pic.twitter.com/YkCMK0rDbf — Erin Boudreau (@Erin_Boudreau) September 15, 2013

Following the CEO's apology, Boudreau wrote, "For what it's worth, I accept @basti's apology. However I don't believe instructing his team to tell me to "f--- off" was a joke or typo."