You asked three specific questions:
Is this possible?
Basically, no. This is literally not possible. The highest-limit prepaid debit cards in existence in the US right now have limits around $15,000. It is, quite literally, not possible to get a prepaid card for $950,000. For that amount of money, you're very deep into the territory of running afoul of money laundering regulations, and it's simply not possible to send a stranger a debit card with $950,000 on it without a significant amount of overhead involved.
It's important to point out that most scammers will use deliberately absurd circumstances in their hooks. They're hoping to catch gullible people, because it's easier to string someone along when they're gullible. A skeptical person (someone not likely to fall for a scam) would see this email and instantly recognize that it seems fishy. So, good for you that you've paused and asked the question instead of just falling for the scam.
I can't understand current situation?
The scammer is trying to fool you into believing that they are gifting you a large amount of money. Once you believe that, they will contact you again and the real scam will start. There are many forms for the actual scam, but they all involve the same eventual result: the scammer gets money from you. This may play out in many different ways, and it's important to not get tricked into comparing your situation to a specific "known scam" because scammers evolve over time, so you may actually be presented with a different trick than the ones you read about on the internet. But, for the sake of example, the next steps often involve things like the following:
- The scammer will employ someone to show up at your door with a uniform and a fancy looking envelope containing the supposed debit card. There may actually be a debit card in the envelope, and they may actually show it to you. However, the delivery guy will tell you that you need to pay him a few hundred dollars to cover the cost of the delivery. This is enticing because he will literally be standing there with "your" debit card in his fancy envelope! So you may be fooled into paying him, only to later find out that the debit card is fake.
- As a variation of that, the scammer may ask you for money to pay for the delivery, upfront. Then you send the money and they disappear.
- The scammer will send you a real, live prepaid debit card, but then they will tell you they "accidentally" put too much money on it, and you need to give them some of the money back. They may instruct you to pay them via electronic transfer (usually a means that's not reversible) or they may even tell you to do something like buy an iPhone and mail it to someone. These transactions may not actually involve any financial loss on your part, and they may actually complete successfully (which sometimes tricks people into thinking the scam was legitimate), but you've just been used as a money mule to help a criminal launder money. Then you go to get "your share" of the money off the card, and either it fails or there never was any more money on it in the first place.
- The scammer will trick you into attaching the card to some other financial account you have. They may ask you to register it with your PayPal account, or do something else that links it to your finances. Then, they use that as a back door to steal your money.
- The scammer will trick you into giving them personal information about yourself at various points in this process. They may even be blatant and ask for your online banking user name and password, or your social security number. Then, they steal your information, or they use your account to help them scam other people.
Ultimately, it doesn't matter how the scam works, because this is quite obviously a scam.
How can I handle this situation?
You should cease all contact with the scammer. If you've already given them any information about yourself (your real name, address, account numbers, social security number, the name of your bank, etc) you should take appropriate action. Change passwords, freeze your credit report, and/or contact your bank as appropriate.
The Federal government maintains a website with information on how to report scams. If you believe you have already been scammed, you should look at that website and report the scam as appropriate. I'm mentioning this because the email you received makes it sound like there was a "prior" transaction.
Also, be ready to receive more random messages from other random people in the future. Scammers keep lists of potential targets. Because you've engaged in conversation with this scammer, you're almost certainly on someone's list. You may be subject to other scam attempts in the future as a result.
Even if you believe you have not had any actual financial loss as a result of this, it's important to be diligent in what you do next, because you may still be at risk in the future as a result of talking with this person.