Who do I contact about receiving unsolicited email/spam in my TA inbox?
In the top right hand corner of your private messages, there's a little red triangle, with an exclamation mark in the middle. This is th same for any post. Click it and write as the reason "spam". A mod will see it and take appropiate action. If the same user is constantly spamming you, I think there's also a way to block them. I think that's the best thing to do.