Notes loss caused by email-account deletion I got a new Macbook yesterday, so I was trying to configure an email account.
At the same time, I recorded some important notes in the "Notes", which were automatically bound to this email account by the system. (which I was not aware of )

This morning, I just found that the email account was not configured correctly, so I deleted it and re-configured a new account.
Then I found that all the notes I recorded yesterday are gone.

Is there any method to recover these notes?
If your notes are really stored in your email account, you should be able to reconnect to the same email account over IMAP to gain access to your notes again. Do not configure the email account as POP3 for example.

However, if you really have a new MacBook, it is probably running El Capitan. With El Capitan notes are no longer stored on IMAP email accounts - in fact it is not supported at all. Most likely your notes are really stored in iCloud, and you need to relogin to iCloud or reenable Notes in the iCloud preferences to access them.