Emails are not triggering for the reviewers

Once a Lifecycle manager got an email that a new asset entered the review status he can open the asset and then he hit the collaboration button for that asset. In the asset lifecycle, the LC manager then add one collaborator and check the email check box for the reviewer. So one collaborator becomes the reviewer for JUST that asset. In this situation the collaborator should be advised by email that he has to review the asset but the mail to notify him that he needs to review the asset is not coming. Instead he got some other mail saying "You have been added as a collaborator for the asset "(Please see the attached screenshot of the mail he is getting). This mail not at all implies that he is also a reviewer of the asset. Though the collaborator is able to find the asset to review in his/her dashboard.
Please let us know if this is a bug so that we can raise it appropriately.