All indications ahead of today's
Not much is known on what Microsoft option will offer, and how it would differ from the popular messaging startup. But that hasn't stopped Slack from going on the offensive.
In anticipation of today's event, Slack took out a full page ad on the back of the New York Times offering Microsoft some "friendly advice."
"Wow. Big news! Congratulations on today's announcements," the ad begins. "We're genuinely excited to have some competition."
The ad continues, telling Microsoft that "it's not the features that matter" and that if they want to do this right they will need to do it "with love."
In addition to the New York Times ad, Slack also posted the text on its website.
This type of friendly tech advertising isn't uncommon in the tech industry. Microsoft even deployed a similar style featuring a chat between Siri and Cortana when it was promoting its ill-fated Windows Phone.
We won't have a wait long for Microsoft to respond to Slack. It's Office event starts at around 11 AM ET.
Follow Eli Blumenthal on Twitter @eliblumenthal