Hi Leonid S , yes this is something we are working on fixing, but would still much prefer to have these kind of notifications as on site notifications than emails. From our perspective it looks pretty unprofessional sending emails for this.

Don't know about unprofessional, but it is definitely much better to send a simple notification on the site, rather than emails. Also, when someone presses the join group link in the invitation email, it just returns a MYSQL error.