If u do not remember your e-mail adress the way to recevery your account is using your recovery key. In the case you lost it too try to use customer support as Borlando recommended.
Edit: Cipsoft just posted a Newsticker about it. It follows:
If you cannot remember the email address of your account, you can now request it via the Lost Account Interface by entering your current password and the account name which was used for your Tibia account before the login process changed on July 02, 2019.
Edit: You also can try to look for your Recovery Key as lehula dohon suggested.
2nd Edit: Today (July, 4th, 2019), Cipsoft added a new section on account lost that will retrieve the email used on a account: https://www.tibia.com/account/?subtopic=forgottenemail&step=showemail
I think you better contact the customer support to find solution.
There is no specific solution for your problem right now.
As explained in other answers, CipSoft got the feedback about this problematic situation, and added option to recover the email address.
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