Mozilla Thunderbird 0.5 introduces a new feature, supporting multiple identities for an account. This is a powerful feature for users who have multiple email addresses that end up in the same mail account. Consider the following scenario:

You have a single mail account which receives email for both a work and a personal address. i.e. thelizard@mozilla.org and partylizard@foo.com. Currently, one of these identities is the identity associated with your account. When sending new mail or replying/forwarding to a message, Thunderbird always uses the one identity associated with the account. This creates confusion, especially when replying to a message sent to the other address since the recipient gets a message from a different address than what they used to send to you. On top of that, you have no easy way of choosing which of these two addresses should be used for a particular outgoing message. Thunderbird only shows you the identity you used to create the account. Multiple identities support to the rescue!

There are several components of this feature:

• When you bring up a new compose window, Thunderbird lists all the identities for all of your accounts in a drop down box. This drop down list now includes all of identities for each account. Now you can easily send a message using any identity for an account by just picking the correct one.
• Intelligent identity detection when replying to or forwarding a message. Thunderbird scans the recipients of the message and chooses the identity the orignal author used when sending the message to you. This identity will then be the default identity in the compose window.
• Different settings for different identities. Maybe you want your work identity to attach a vCard, and your personal identity to attach a signature. By allowing multiple identities to be attached to the same account, the user can customize the properties of each identity for that account.

Setting up Multiple Identities

This sounds fantastic, surely there is a catch? Yes, there is a catch. We have not developed UI in Thunderbird to configure multiple identities yet. You must be comfortable modifying user prefs.js in order to take advantage of this feature. Before beginning, make sure you are familiar with how to edit config files. You should also know where to find your pref.js file in your profile directory.

I am assuming you already have a Thunderbird profile with your accounts already set up. Make a backup copy of prefs.js in case you make a mistake and need to go back.

Creating the new identity

Open up prefs.js in your favorite text editor. Look for a set of identity prefs with the following form:

"mail.identity.idX."

where 'X' is a number like 1, 2, 3, etc. Pick the set of identity prefs which are already associated with the account you want to add a new identity to and make a copy of all the prefs that are prefixed with the identity you picked (i.e. "mail.identity.id1"). Change the number to the next available integer. Make sure you are not using an integer that is already used by another set of identity preferences.

Tweak the settings for this new identity according to taste. You may not need to change many of these settings from the one you copied. In particular, don't forget to change the .useremail attribute to the email address associated with this identity. You may want to associate things like a vCard or a signature with this identity. I found it easiest to go back to the account manager, create a vCard/signature for an identity then open up prefs.js again and copy the resulting vCard/signature preference string into the new identity prefs. You should now have a new identity that is not attached to an account yet that looks similar to the following (remember id# is really id followed by an unused integer chosen by you)

        user_pref("mail.identity.id#.doBcc", false);
        user_pref("mail.identity.id#.doBccList", "");
        user_pref("mail.identity.id#.draft_folder", "SOME URL YOU DON'T NEED TO CHANGE");
        user_pref("mail.identity.id#.drafts_folder_picker_mode", "0");
        user_pref("mail.identity.id#.encryption_cert_name", "");
        user_pref("mail.identity.id#.encryptionpolicy", 0);
        user_pref("mail.identity.id#.fcc_folder", "SOME URL YOU DON'T NEED TO CHANGE");
        user_pref("mail.identity.id#.fcc_folder_picker_mode", "0");
        user_pref("mail.identity.id#.fullName", "YOUR NAME");
        user_pref("mail.identity.id#.organization", "YOUR ORGANIZATION");
        user_pref("mail.identity.id#.overrideGlobal_Pref", true);
        user_pref("mail.identity.id#.reply_to", "");
        user_pref("mail.identity.id#.sign_mail", false);
        user_pref("mail.identity.id#.signing_cert_name", "");
        user_pref("mail.identity.id#.smtpServer", "smtp1");
        user_pref("mail.identity.id#.stationery_folder", "SOME URL YOU DON'T NEED TO CHANGE");
        user_pref("mail.identity.id#.tmpl_folder_picker_mode", "0");
        user_pref("mail.identity.id#.useremail", "SOME EMAIL ADDRESS");
        user_pref("mail.identity.id#.valid", true);
      

Linking the identity to an account

Now that you have created an identity, you need to bind it to an account so it shows up as one of the multiple identities for that account. Find the account you want to add the identity to. It should have the following form:

mail.account.account#

where '#' is an integer. Be sure to find the right account. Now modify the .identities preference for that account, appending the new identity we just created after the default identity for the account. You can append as many identities as you want / have created.

user_pref("mail.account.account##.identities", "id1,id#"); where # is the number of the new identity

Now save prefs.js and launch Thunderbird. Bring up a compose window. If you set everything up correctly you should see the email address for this new account listed in the From: drop down box. Reply to a message which was sent to the email address used by your new identity. You should see it get pre-selected in the from field.

If you need help setting this up, ask in the Mozillazine forums.