That is a great feeling to get those emails just this past month I received about 7 different account raises but only received one email on one account the others were just a pleasant surprise after logging in and seeing the limits raised
Always great getting these emails. Sometimes they don't send email and you just notice when logging in though. Good reason to keep checking dormant accounts though
I'm pretty sure I know exactly why I got this email, but don't want to spill the beans and expose myself. But let's just say it survived some limitation that other accounts did not