The difference is that the alias provider or destination email provider can associate all your accounts with your identity. I do not want to give this ability to either the alias provider or the email provider. It is a different threat model. (Please correct if I am wrong)
I did not say how many different accounts I have, but you can assume my separation of accounts is sufficient for my needs.
I should clarify that I already have multiple email accounts, so extra aliasing is not necessary. I’m looking for an email client application I can run on my desktop which separates the accounts well enough from the email provider.
To be honest, I didn’t verify the signature when I installed it. The download is over TLS (HTTPS) so you know you have a secure connection with the F-Droid server during the download. But because of the tiny chance the F-Droid website was hacked at the time you download it, you should verify the signature.
I’m having a hard time finding how to access about:profiles, but in looking for this I found you can disable the “download messages on startup” option. Maybe Thunderbird is the solution. It will require some more investigation, but this is giving me hope.