another options is to buy a domain with a cpanel and set up a forwarder and filter to a specific folder in your secret main email account. The extra benefit here, since you own the domain, is that you can create a send identity of your [email protected]
[email protected] is the same as [email protected]
[0]: https://www.fastmail.help/hc/en-us/articles/360060591053-Plu...