Slack is the industry standard for managed instant messaging (IM). A good alternative would be to self (or cloud) host an open source IM such as Mattermost but as always it would be a good idea to do a cost benefit analysis between the solutions.

Some of the main things to consider:

• Having a good SDK for plugin creation
• Having good integrations with existing tools ( JIRA , GitHub , OpsGenie , etc.)
• Cost
• Maintenance and administration
• Covers all your businesses use cases