a week ago
Probably....have you actually sold anything that may need to be posted off?
Any e-mail "from eBay" that doesn't come from an ebay.com or ebay.com.au address (or variations depending on country) is fake.
Was this only in your emails or was it also in your actual ebay messages too?
Sounds very much like a scam to me
If it needs to be sent to Nigeria, it is certainly a scam. Contact ebay and let them know.