The long-running contest between Microsoft and its Teams service and Slack’s eponymous application continued this morning, with Redmond announcing what it describes as its first “global” advertising push for its enterprise communication service.

Slack, a recent technology IPO, exploded in the back half of last decade, accreting huge revenues while burrowing into the tech stacks of the startup world. The former startup’s success continued as it increasingly targeted larger companies; it’s easier to stack revenue in enterprise-scale chunks than it is by onboarding upstarts.

Enterprise productivity software, of course, is a large percentage of Microsoft’s bread and butter. And as Slack rose — and Microsoft decided against buying the then-nascent rival — the larger company invested in its competing Teams service. Notably, today’s ad push is not the first advertising salvo between the two companies. Slack owns that record, having welcomed Microsoft to its niche in a print ad that isn’t aging particularly well.

Slack and Teams are competing through public usage announcements. Most recently, Teams announced that it has 20 million daily active users (DAUs); Slack’s most recent number is 12 million. Slack, however, has touted how active its DAUs are, implying that it isn’t entirely sure that Microsoft’s figures line up to its own. Still, the rising gap between their numbers is notable.

Microsoft’s new ad campaign is yet another chapter in the ongoing Slack vs. Teams. The ad push itself is only so important. What matters more is that Microsoft is choosing to expend some of its limited public attention bandwidth on Teams over other options.

Stock

While Teams is merely part of the greater Office 365 world that Microsoft has been building for some time, Slack’s product is its business. And since its direct listing, some air has come out of its shares.

Slack’s share price has fallen from the mid-$30s after it debuted to the low-$20s today. I’ve explored that repricing and found that, far from the public markets repudiating Slack’s equity, the company was merely mispriced in its early trading life. The company’s revenue multiple has come down since its first days as a public entity, but remains rich; investors are still pricing Slack like an outstanding company.

Ahead, Slack and Microsoft will continue to trade competing DAU figures. The question becomes how far Slack’s brand can carry it against Microsoft’s enterprise heft.