For UA, You will have to create another account with the email that you wanted to change.
For PN, you may write your request here.
But I have active ads in my current account, what should I do?
You will need to sign up for a new account under your new email. We will then transfer all the accounts from your previous account to the current active one. You write your request here if you have an active ad in your previous account.
What will happen once the ads transfer is done?
Once the transfer is done, all your previous chat messages from buyers or sellers from your previous email will also be deleted.