## Overview Before a campaign or account email goes out, someone usually has to check it in Gmail, Outlook, Apple Mail and on a phone. The people who sign it off, such as the marketer, the designer and the developer, often work in Slack rather than in a testing dashboard. Copying screenshots into a channel by hand makes it easy to review an old version or miss the one client that broke. MailSlurp renders your email on real email clients and devices and captures a screenshot of each. The MailSlurp Slack app posts those results to the channel you choose, so the team sees which clients passed and can approve the email or ask for changes without leaving Slack.

Add to Slack

The button opens the Slack setup page in MailSlurp, which connects your workspace to your MailSlurp account. Sign in or create a free account first if you do not have one. ## What the Slack app posts Each render message names the email and shows how the render went: - a message when a render starts, finishes, partly finishes or fails - a line for every email client, such as "Gmail on Android: ready" or "Classic Outlook on Windows: failed", with the reason when a client fails - a **View render** button that opens the full results - optionally, one screenshot per email client as a reply in the message thread - optionally, **Approve** and **Request changes** buttons for reviewers Screenshots and the **View render** button use a share link, so people in the channel can open the results without a MailSlurp login. ## Connect a workspace 1. Open **Device previews** > **Notifications** > **Slack** in MailSlurp, or use the button above. 2. Choose **Connect Slack**, pick your Slack workspace and review the permissions. 3. Choose **Allow** to return to MailSlurp. 4. Load your channels and add the channel that should receive render results. ![Slack asking to allow the MailSlurp Notifications app to access a workspace, with the permissions it requests](/_astro/slack-oauth-approval.Bl3rzKue_Z12QrJc.webp) The app asks to post messages, including to public channels it has not joined, and to list your public and private channels so you can choose one. To post to a private channel, invite the MailSlurp Notifications app to that channel first. ## Choose what gets posted Open **Device previews** > **Notifications** and create a rule for the Slack channel. Choose the events to send, for example **Completed** and **Failed**, then open **Options** to turn on: - **Include thumbnails** to show the main screenshot in the message - **Post screenshots by client** to reply in the thread with a screenshot for each email client - **Ask for approval in Slack** to add the **Approve** and **Request changes** buttons Use **Test** to send a sample message and check that it arrives in the right channel. ## Approve or request changes When a render finishes, anyone in the channel can review it: - **Approve** records the approval and updates the message to show who approved it. - **Request changes** opens a short form. Pick the email client that needs work, if it is specific to one, and describe the problem, for example "The logo disappears in Outlook dark mode". The comment is saved on the render, and the message updates to show the request. Reviewers can change their decision later, for example approving after a fix. The full review history appears on the render page in MailSlurp, where teammates can also approve or request changes directly. To tell the email's owner when a decision is made, create a second rule with the **Approved** and **Changes requested** events, sent to their channel or another destination. ## Troubleshooting If a message does not arrive: - check that the rule is enabled and the destination is active - invite the app to the channel if it is private - send a **Test** message from the rule - reconnect the workspace if the Slack app was removed For other alert types, such as quota and billing alerts, see [notifications](/docs/notifications/). To learn more about rendering, see [device renders](/docs/device-renders/).