IF you got the message to your eBay message box, with eBay headers - it is from eBay.

IF you did NOT get the message in eBay, you simply received it in your email - it could be a scam.

Here is wording directly from eBay ...

Here's some information about: How to know the email you received was sent by eBay
Here are some things to watch out for:

eBay will never ask you to provide account numbers, passwords, or other confidential information through email.
If we do request information from you, a copy of the email will also appear in the My Messages section of My eBay. If you don't see a copy there, the email isn't authentic.
In addition, spoof emails often:

begin with a general greeting such as "Welcome eBay User," rather than your name or user ID
claim that eBay is updating its files or accounts -- this is a common tactic of spoof email
contain an "urgent" warning, telling you that your account is in jeopardy and you won't be able to buy or sell on eBay if you don't provide personal information immediately.
Even links that go to real-looking pages can be fake. Never click a link in a suspicious email. Sign in through the usual process.
If you suspect an email is fake, please forward it to us at spoof@ebay.com.
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If you have given out personal information and it fits being a spoof - take measures to protect yourself on the information you gave.

IHOPETHISHELPS
Paul