Here's an advice for Manda, DON'T rely on their notifications, ever. They come way too late, if at all, and they leave too much time for others to outspeed you. The fastest way of knowing if your desired product came in is to monitor one of the listings directly, particularly this bottom section here.
As example, the other day I snatched a sofubi I was waiting on using this method. Its stock status updated on the bottom of a sold listing that I was refreshing once or twice an hour but it didn't show up in the tags or anywhere else until about 2-3 hours later. The notification never came at all even though I made sure all the alerts were on and it's not in my spam box. It's not convenient but honestly I'm glad it's like this, it gives the upper edge to those few who know exactly how the site's stock update system works. I got so lucky this time, if I didn't randomly wake up in the middle of the night and decide to check on the status I'd probably have missed it.
That said, I still recommend checking one of the tags in tandem with the listing just to be safe. On rare occasions Mandarake makes a whole new, separate listing for the same item they already had in stock before and when they do that it isn't going to show up in the bottom of the previous pages of this item. Another thing to note is that Mandarake does update during their closed hours but not as actively and for the most part it's only within the first 3-4 hours after they close.