That is an automailer that will just answer the following:
Thank you for reaching out to Rocket.Chat. We will respond to your email as soon as possible.
If your email is about reporting a security vulnerability, we kindly ask you to directly submit the report into our Hackerone program here: HackerOne
Once you have submitted there, we will follow up directly in Hackerone.Regards
The Rocket.Chat Security Team
I’m starting to believe they haven’t had a security team for the last two years.