FastMail & Exisiting Website Accounts

Hey dwestenk, sorry for the delay in our response. I'll answer your questions below:

I have numerous website accounts with the same email username. To change the username for each account, do I need to change it at the account profile with an alias generated in FastMail and then edit the 1Password username field with the generated alias?

Yes, you would have to sign into your account websites, go to the username change page, and update your username there. However, you do not need to edit the login and add your generated alias to it. As you update your username on an account website with a Masked Email, you should be prompted by the 1Password extension to update the login. Just select to update the login, and you'll be all set.

Here's an example of how that works when changing a username on Amazon.com: https://share.cleanshot.com/mBYDT7Zg

Please note that if the prompt contains your old username, you can simply delete it and then update the login.

If so and I receive unwanted messages at a Masked Email, can I block incoming email for it

Yes, you can block incoming emails once you save a Masked Email to a login. Here's the direct link to the steps on how to do that: https://support.1password.com/fastmail/#manage-masked-emails

I hope this helps! Let us know if you have any other questions.