Slack Technologies Inc.’s team chat service was hit with a widespread outage earlier today that left affected users unable to access the service for about five hours.

The issue has since been fixed. However, at some point during the outage, Slack’s email notification feature and calendar integrations started experiencing problems that at the time of writing aren’t yet resolved.

More than 12 million people logged into Slack every day when the company last shared its daily active user count in September 2019, a figure that has since likely increased sharply with the shift to remote work. At 10:14 a.m. EST today, the company posted a message to its service status page stating that “customers may have trouble loading channels or connecting to Slack at this time.”

About 70% of the thousands of users who reported the incident to outage tracking service Down Detector today are said to have encountered difficulties logging into Slack. An additional 28% couldn’t send messages.

After the initial post flagging the problem, Slack’s engineers started sharing updates on their troubleshooting efforts every 30 minutes. They reported the first improvement at 1 p.m. EST, writing that “some customers may be able to connect, but may also experience degraded performance.” The following update informed users that they should avoid refreshing Slack if they had successfully launched the client. Finally, at around 3:10 p.m., Slack managed to restore service.

But the recovery didn’t go completely smoothly. At 1:51 p.m., in the same message that advised users not to refresh Slack if they had managed to launch the service, the company disclosed a problem with its email notification feature. The latter issue is ongoing and appears to be preventing some users from receiving email notifications for items such as direct messages that normally trigger an alert. Slack also said that the integrations it provides for Google Calendar and Outlook Calendar “aren’t working as expected.” 

Slack’s service disruption today marks the latest in a series of outages to have hit widely used cloud applications over the last few weeks. Previously, Gmail, Maps and other popular Google LLC products briefly went offline because of an issue with an internal system responsible for processing logins. The same day as the Google outage, some users reported issues accessing Microsoft Corp.’s popular Outlook email service. 

Photo: Slack