Mailcow: Add a recovery email address so users can reset their passwords

• you need the admin credentials of the email system
• log into https://admin.galae.net/domainadmin/mailbox with admin credentials
• click on the tab 'Mailboxes'
• the URL should be https://admin.galae.net/domainadmin/mailbox
• find the email address for which you want to add a recovery email address
• on the row of that email address, click '+ Edit'
• you should be on the page https://admin.galae.net/edit/mailbox/username%40domain.tld
• on the row 'Password recovery email', add the recovery email address
• click 'Save changes'