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Slack Technologies (WORK) shares plunged Thursday after the business messaging group indicated slower near-term sales growth even as it topped Wall Street forecasts in it first quarterly earnings as a public company.

Slack said it posted a loss of 14 cents a shares for the three months ending in July, the group's fiscal second quarter, a tally that topped the Street consensus of 18 cents per share. Group revenues, Slack said, rose 58% from the same period last year to $145 million, well ahead of the consensus estimate of a $141.2 million tally, even as Slack offered $8 million in credit to customers affected by system outages that occurred over June and July.

"Customers don't have to request it, we just proactively give it," CEO Daniel (Stewart) Butterfield explained to investors on a conference call late Wednesday. ""e give those service credits to every customer even if they were not specifically affected. So those policies are outrageously customer-centric, which is part of our background and our orientation. And that is one of the reasons you see that effect."

"It's not necessarily proportionate to the outage, because if we had the same (sales and licensing agreement) as Salesforce (CRM - Get Report) or Microsoft (MSFT - Get Report) or any of our peers in the industry, we wouldn't have paid out anything ... t's our policies that make a difference," he added.

Slack shares were marked 16.09% lower Thursday to change hands at $26.10 each, a move that would pull the stock to within a dime of its June 21 IPO price of $26 per share.

Looking into the current quarter, Slack said it sees group revenues in the region of $154 million to $156 million, a figure that would indicate growth of around 47% from last year, and a non-GAAP loss of between 8 and 9 cents per share. For the full year, however, Slack boosted its revenue guidance to a range of between $603 million and $610 million and improved its 2019 loss outlook to between 40 and 42 cents per share.

"We believe Slack guides very conservatively, as is normal for recent software IPOs. We note that Slack exceeded its guidance, in spite of the outage, which we do not believe was factored into guidance," said DA Davidson analyst Rishi Jaluria.

"We like Slack for its near-ubiquitous nature, rapid growth, secular tailwinds, and large market opportunity, and our due diligence is very positive," he added. "Valuation, however, keeps us on the sidelines and we would advise investors to wait for a pullback before establishing a position."