It depends. If it's not exposed to a network and doesn't have any awful bugs, than it should be fine.
Usually those mailtrap servers have some exposure to the company intranet or sometimes the internet, which could be problematic. Even test systems might receive sensitive data in the emails, that shouldn't be leaked to an attacker. An unmaintained software might have well known security issues.
Usually those mailtrap servers have some exposure to the company intranet or sometimes the internet, which could be problematic. Even test systems might receive sensitive data in the emails, that shouldn't be leaked to an attacker. An unmaintained software might have well known security issues.