Of course, email accounts are separate accounts that should have their own environment, but if you want, you can set up [[Organize Your Messages by Using Filters|message filters]] in Thunderbird to copy particular messages to another account’s folders, e.g. based on To, recipient, domain, just name it. You could also consider setting up email forwarding (as a ''copy'', if possible) at the email provider using their webmail portal, depending on your demands. It’s also possible to use the ''Unified folders'' view - see the [[Switching the folder pane view]] article for more info.