When you @mention an invited member or send them a direct message, they'll receive an email notification. We're also working on a feature that will allow invited members to reply to messages in Slack by email.
If an invited member replies to an email notification, their message will be sent to the appropriate channel, thread, or direct message in Slack.
Once an invited member joins your workspace, they'll see any channels they belong to and their direct messages so they can continue collaborating in Slack.
Note: If invited members unsubscribe from email notifications, it won't have an impact on their invitations. They'll still be able to join your workspace in the future.
Manage invited members
Accounts and billing
While an invited member can receive email notifications and reply to messages in Slack via email, they do not yet have an active Slack account. An invited member's account becomes active when they accept their invitation and sign in to your Slack workspace for the first time.
If you're on a paid plan, you will not be billed for invited members until they become active in Slack.
Workspace Owners and Admins can manage pending invitations from the Manage members page. Enterprise Grid Org Owners and Admins can manage invitations from the admin dashboard.
When you add people to Slack using SCIM provisioning, pre-provisioned invited members will be visible in Slack as soon as they're added via your identity provider (IDP). Until they sign in for the first time, they'll receive emails whenever someone in Slack notifies them. They can also reply to Slack messages by email. Users provisioned with just-in-time provisioning will not be visible in Slack until they log in.
If you revoke an invited member's invitation, their Slack account will be deactivated and they'll stop receiving email notifications. Should you re-invite them to Slack in the future, they'll be treated as a new invited member until they join your workspace.
Email notification settings
If you're on the Plus or Enterprise Grid plan, whether or not invited members can see contents of Slack messages in email notifications depends on your settings.
Invited members will not see message content in these scenarios:
Their email domain doesn't match other members and SSO is enabled for your workspace or org.
Their email address is hosted by a domain you've blacklisted for your workspace.