An email alias is an email address that forwards to another email address. For example, if your primary email address is "js@example.com", you might create a second email address called "johnsmith@example.com", which is easier for people to remember. Messages sent to your "johnsmith@example.com" account would then be forwarded to your "js@example.com" account.

The ability to create email aliases depends on your email provider. Once you have set it up (probably through your provider's website), you can configure Thunderbird to download and sort messages to your alias account in the same manner it deals with messages to your primary account.

Configuring an account to deliver messages to your Inbox

The following example shows how to configure a Hotmail / Windows Live Mail account to place messages to your email alias in your inbox. Other email providers will usually have an equivalent interface.

1. Sign in to your Hotmail account with a web browser.
2. Click Options and then click More options....
3. Under Customizing Hotmail, click Rules for sorting new messages to configure how new messages are sorted.
4. Delete the rule that places new messages into its own folder.

Using Identities to specify a reply-to address

When you reply to a message that was sent to your email alias, you may want the reply address to be your alias address rather than your primary address. You can use Thunderbird's Identity functionality to configure this.

1. In the Thunderbird account settings (Tools > Account Settings...Edit > Account Settings), click on your primary account name.
2. Click the Manage Identities... button, and then click Add....
3. Enter the name you want to associate with the alias email account.
4. Enter the alias email address as both the email address and the reply-to address.
5. Review the settings on the other tabs. You can configure various options, such as reply quoting, location where messages should be stored, encryption, etc.
6. Click OK to close the dialog and click OK again to close the identities list.

Storing messages to an email alias address in a separate folder

Instead of storing messages sent to your email alias in the standard Inbox, you can configure Thunderbird to store them in their own folder.

1. Select File > New > Folder... from the menu.
2. Enter the name of the folder you want to create.
3. Select the location where the folder should be created, and then click Create Folder.
4. Back in the main Thunderbird interface, select a message that has been sent to the alias account.
5. Click Message > Create Filter From Message....
6. In the filter dialog, enter a name for the filter and make sure that it is configured to apply when Checking Mail or Manually Run.
7. Configure the filter so that the To is the alias email address.
8. Set the action to Move Message to, and then select the folder you created above.

Messages will now be automatically stored in the designated folder on arrival.