Mail app deleted my accounts and mailboxes

Today, I turned on my Mac, opened Mail and it asked me to "add account". Without any reasons, all my mailboxes disappeared! Like if I was installing a new Mail app.

I have my mails and mailboxes on Library > Mail > V2, so how can I restore things exactly as they were?

PS.
- I don't have Time Machine installed.
- I have 10 accounts, so importing each .mbox file is insane. Is there other way?

 

I had to do account by account... How do I delete this thread?