It's a very well-know scam that's been doing the rounds for years. Criminal gangs trawl the web targeting new and inexperienced sellers of electronics and other valuable items (especially those who, like you, use totally the wrong postal service as that makes them look even more inexperienced).
If you give them your email addy, you'll receive a fake PayPal payment confirmation email, advising you've been paid and it's safe to ship. This ages-old scam still works because some sellers fail to check their PayPal accounts to see if the money is actually there. Which of course it isn't.
Ignore and delete, and upgrade your postage to Special Delivery Next Day Guaranteed, which is essential for all items valued at over £50. Standard 1st and 2nd Class only cover items valued at up to £20 - so if the phone is lost or damaged in transit, you're stuffed. But you will have to refund the buyer in full.
If you clicked on any links in these emails, check your device for malware, and then change all your passwords.
@leshar-2982
