A Manhattan boutique owner who dresses stars such as the Kardashians and Katy Perry is suing her e-mail provider — for making her high-end clients think she’s been ignoring them.

Alison Brettschneider, who owns 25 Park on the Upper East Side and a Bridgehampton outpost of the shop, has had a business e-mail address for 10 years through a Queens-based server called Digital Data Factory.

Recently, Brettschneider has been arguing with the Data Factory’s owner, Andrew Kupiec, over “inflated, inconsistent and confusing billing and invoices,” her suit says.

Suddenly, on May 11, Kupiec cut off the boutique owner’s access to her e-mail. Brettschneider says she sued because she couldn’t reply to the hundreds of messages that were piling up in her inbox.

She’s suing for $1 million. A judge ordered Kupiec to restore access while the case is pending.

His attorney, Elio Forcina, said Kupiec blocked Brettschneider’s e-mail over a $5,590 bounced check.