Your Apple ID was used to sign in to iMessage on an iMac 27" named “lijy的Mac”.

Just change your Apple ID's password here: https://appleid.apple.com

To make your Apple ID more secure use 2 factor authentication, read here: Two-factor authentication for Apple ID - Apple Support

To be safe, reset your password through your settings. iOS devices: settings>tap name>tap password and security>tap change password>enter passcode>create new password>tap 'sign out of all other devices' when prompted...and yes, change your security type to two factor in settings>password and security, if already haven't.

If this is a phishing attempt, you can forward email to reportphishing@apple.com. The security team will investigate.

Send the e-mail to Apple as an attachment to a new e-mail before deleting it. You can forward as an attachment by going to Mail/Message/Forward as attachment. You won’t receive a response.

reportphishing@apple.com

Could be a scam. When I click that link it goes nowhere!

I would disregard and delete.

ASC - Late 2012 Mac mini, macOS 10.14.5; Watch, series 3 cellular, watchOS 5.2.1; iPad Air 2 & iPhone 8+, iOS 12.3.2; TV 4th Gen, tvOS 12.3;  HomePods, audioOS 12.3 and Airport Express w/ Airplay 2