That seems suspicious; in particular, you don't publish your email address on the site that I can see. The IRB email address looks legitimate (andrew.cmu.edu is the main domain at CMU), so you might forward it there to ask.
I personally know one of the researchers listed there and will pass along a link to this post.
Update: I asked one of the listed researchers, who confirmed to me that the project is legitimate and put me in touch with Maria Tomprou, the PI (using a CMU email address). Maria explained that they sent out the email from their lab account but followup would come from CMU. The researcher I contacted has also asked the IRB to make a searchable list of approved projects available online.
Here are some excerpts from Maria's email to me (quoted with permission):
This is the project that I am responsible for. We have received an IRB approval about this. Please see the attachment. We use the gmail account of our lab (Connected Experience or CoEx) that we have created for research purposes and if participants contact us, we use our regular cmu e-mail.
Attached was an IRB approval form signed by John Zimmerman, IRB Chair.
Also in the momentum to reduce any inconvenience I might have caused to you or the Users, I completely skipped to offer some background about my project and its importance.
Online communities like Workplace have completely transformed the meaning of career advice seeking and offering compared to more traditional forms of mentoring (e.g. with your supervisor, peers) that may hinder your career or offer biased advice (often called the dark side of mentoring). So we want to gain a deeper understanding of the mechanisms such as motives, usefulness, attributions of how this new form of mentoring functions as well as the impact of the advice from Workplace channel on people’s careers. How does this online community impact User’s career trajectories, negotiations, finding a job, changing careers etc? Does Workplace replace the traditional mentoring? All these are important issues not only for the role of online communities but also what organizations can learn and benefit from these kinds of communications.