This is a legit e-mail. You received it because you responded to an e-mail notification of from the forum that you had received a PM.
Those notifications are automated and when you respond to them (by hitting the reply button) your response goe to our helpdesk. The help desk is for tech support issues like account changes. When we receive a message at the help desk we issue (again automated) a reference number (ticket number) to help us track your issue. This number is sort of like taking a customer service
number at the bakery or licensing office.
You can ignore all this - but the mail is not malicious, nor spam. Social Knowledge Networks is the parent company of this forum.
I removed your e-mail address from the post you made. When you post your e-mail address online, you open yourself to all kinds of spam.