Zipwhip, the Seattle-based provider of toll-free messaging for businesses, will be acquired by digital communications firm Twilio for $850 million in cash and stock, the companies announced Monday.

The deal is expected to close by the end of the year.

Both companies build software to help businesses communicate with customers, in part by creating automated text messaging campaigns. Twilio helps businesses send and receive over 105 billion messages a year, the company said in a news release.

Zipwhip, which says more than 30,000 clients use its technology to send text messages from their landline phone numbers, employs roughly 260 Seattle employees in its Lower Queen Anne offices.