(Bloomberg) -- Stamps.com Inc., the online postage company, has agreed to be acquired for $6.6 billion in cash by private equity firm Thoma Bravo.

The purchase price of $330 a share is a 67% premium to Stamps.com’s Thursday closing price, the companies said in a statement Friday. The stock had stalled so far this year, with a 0.8% gain, but surged 135% last year.

After a brief trading halt, Stamps.com’s shares jumped 65% to $326.47 in premarket trading Friday in New York.

The deal includes a 40-day “go-shop” agreement allowing Stamps.com to seek a higher offer, the companies said.

Thoma Bravo has carved out a niche within the buyout industry, focusing on cloud software businesses that draw steady, recurring sales in the form of subscriptions. The firm makes light-touch operational tweaks to the companies it acquires, usually keeping existing management in place and concentrating on growth rather than cost-cutting.

Along those lines, the companies touted the experience of Stamps.com’s management team in Friday’s statement. The e-commerce company, a pioneer in digital postage, will remain based in El Segundo, California.

J.P. Morgan Securities and law firm Proskauer Rose advised Stamps.com, while Kirkland & Ellis gave legal advice to Thoma Bravo.

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