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Slack is one of the most widely used messaging platforms in the world, with millions of daily active users. In order to ensure the continued smooth functioning of the service, Slack recently sent out an email to all its users asking them to ensure that a new root certificate is installed in their infrastructure for the domain by May 9th, 2023.

This email has caused some confusion and concern among users, with many wondering what is and why they need to install a new root certificate for it. Some users have even expressed suspicion that the email might be a phishing attempt.

In reality, however, is a legitimate domain used by Slack for serving certain types of content. The new root certificate being requested is necessary because Slack is switching its certificate authority (CA) from a major provider to Let's Encrypt. The new CA requires a different root certificate, which is why Slack is asking users to install the "ISRG Root X1" certificate from Let's Encrypt.

The reason for the switch to Let's Encrypt is likely related to its focus on security and privacy. Let's Encrypt is a non-profit certificate authority that offers free SSL/TLS certificates, which are used to secure websites and other online services. By switching to Let's Encrypt, Slack is making a statement that it takes security and privacy seriously and wants to ensure that its users' data is protected.

While the email from Slack may have caused some confusion, it is important for users to follow the instructions and ensure that the new root certificate is installed by May 9th, 2023. Failure to do so could result in issues accessing Slack or potentially even security vulnerabilities.

It is worth noting that the new root certificate being requested is not specific to Slack. Let's Encrypt is used by many websites and online services, and the "ISRG Root X1" certificate is likely already installed on many computers. However, it is still important for users to check and ensure that the certificate is installed and trusted on all systems that access Slack.

In conclusion, is a legitimate domain used by Slack, and the request for a new root certificate is necessary due to the company's switch to Let's Encrypt as its certificate authority. Users should follow the instructions in the email and ensure that the new certificate is installed by May 9th, 2023, to avoid any potential issues accessing Slack or security vulnerabilities.