users:read.email scope

Your Slack app may gain access to email addresses belonging to team members in a workspace by asking for users:read.email. This scope is now required to access the email field in user profiles retrieved with the Web API when using user or workspace tokens. Classic bot tokens are granted access to the email field without needing further scopes.

This scope must be requested at the same time as users:read.

Accessing email addresses
The users:read.email OAuth scope is now required to access the email field in user objects returned by the users.list and users.info web API methods. users:read is no longer a sufficient scope for this data field. Learn more.