Missing Alias in Mail

schroederfoto,

Thanks for the update and additional details.

If you head on over to iCloud.com (iCloud), are you able to select the alias to send an email from there? Once you sign in and click on Mail, you might need to open Preferences, which is the gear icon next to the refresh arrow near the top-left side. Then, click Composing to see if you see your Alias under Send From.

Keep us posted.

Best regards.

Hey schroederfoto,

Thank you for using the Apple Support Communities! We understand you're unable to use an alias to send emails because you don't see it listed as an option in Mail. We'd like to help.

Which macOS are you using? Did the other alias only go missing after creating and adding a new alias?

How many alias do you have added in total? Per Add and manage email aliases for iCloud Mail on iCloud.com, "After you set up a primary iCloud Mail address, you can create up to three @icloud.com email aliases on iCloud.com."

Are you using these steps: Use email aliases in Mail on Mac

Best regards.

schroederfoto,

Perfect! Glad to hear that got the job done!

Take care and stay well.