hacked

Dear Thunderbird, my Email has been hacked and im now seeking help.. i don't know how to recover it, since i never made a recovery code.. the only way i am able to provide evidence of me owning the mail, is the mail address and the old password. however i am still signed in on the mail on my phone, but unable to send/receive mails. I can see all my recent mails, but not open/access them. When I got hacked, the hacker sent a mail to myself telling me I was hacked, perhaps this could be some sort of evidence to help me? the email this letter is referring to is: [edited from public] @chjensen.dk Best regards Mikkel Jensen.