Since we are using a third party for billing, there's no way at Ahrefs to change your login e-mail for a functioning account.
The only way to do it is to cancel your current subscription and re-subscribe with an updated e-mail address.
Alternatively, you may still keep your current email for logging in and change your e-mail correspondence for invoices and billing notifications. For this please drop us a request via chat or drop us an email to firstname.lastname@example.org.
Or, you may change your e-mail for alert notifications. But do note that by default, the login e-mail is preset each time you set up your alert notifications and you will need to manually change the e-mail for each of these notifications.