Thunderbird's Most Underrated Feature: Identities


There are many good reasons to use Thunderbird 2 as your default desktop email client. Mozilla’s Thunderbird feature page lists some of them: advanced views, decent searching, security, junk mail screening, RSS feeds, add-on plugins and themes, cross-platform versions, and more.

However, there is one feature in Thunderbird that gets less press, yet is handled so beautifully as compared to other desktop clients it’s about time someone stood on a platform and sang its praises: identities. If you have ever had another email address ( forwarded to your “main” email ( and have been frustrated that your replies are appearing to be from instead of, you’ll want to understand how this underrated gem works.

First of all, you’ll need to be sure that the SMTP (outgoing) server you are using isn’t picky about what’s in the “From” field of your outgoing messages. Some ISPs (and hosts) will only allow you to send email through their server with a “From” domain that matches their email accounts. Identities probably won’t work in this case. I forward all of my email, both work and personal, through to an Island Email account (for spam cleansing) whose SMTP server does not have any problem with alternate “From” addresses. Authentication is by username & password.

In Outlook, and other desktop email clients you can easily set up multiple signatures and multiple accounts, using the “from” email address that you want to appear in your outgoing message. You just have to be careful that account is not checked to download new mail on a schedule (since you only care about outgoing messages for that account), and you have to remember to select the correct account/signature on each message that you want to appear to be coming from that address. So if you hit reply on an email addressed to but it was received from the account, it will use as the “From” address along with the signature set for that account unless you manually change the account to before sending the message.

With Thunderbird, you do not have to remember to manually select the account you want. Thunderbird will look at the email the message is sent to, and will automatically select the proper identity when you reply. If you manually switch identities on your outgoing message, the signature file, formatting preferences and what will happen to the message after you send it switches on-the-fly.

Mozilla, you had me at hello.

Start with the default identity, and click the “Manage Identities” button on the screen:

You’ll see the default identity you established above. Click “Add…” to create a new one.

Enter in the information you want recipients to see. The key to identities is that you’re not entering the server address or username. It’s only about outgoing messages, and it links the outgoing action based on a matching email address in a received message’s “To:” field. How smart is that? This is much easier and more powerful than setting up a complicated system of accounts, filters and rules that act on that field.

Here you can tell Thunderbird what to do with email that is sent from that identity. Maybe you have a separate folder just for sent mail from that alternate address? Outlook or would require you to set up a separate rule/filter to make sure those messages are filed separately. Thunderbird makes that easier.

Finally, you can change the formatting of your post and quoting style based on the outgoing identity.

Think about compiling all your various email accounts into one bucket, and then using this feature in Thunderbird to effortlessly switch back and forth between all the different email accounts you have, with only one mailbox to check and manage. Hit “reply” to an email addressed to a work-related address without worrying about your casual, personal contact information accidentally left at the bottom as you juggle signature file settings.

Personally, this is the killer Thunderbird feature that is the reason I haven’t launched Outlook in nearly a week. It’s not even new to Thunderbird 2. It was introduced in Thunderbird 0.5 (without the GUI to easily manage it). I just didn’t realize it existed before.

What’s your favorite underrated Thunderbird feature? Share in the comments.



Hi, do you know how to set Thunderbird’s multiple identities so that it does not only link the outgoing action based on a matching email address in a received message’s “To:” field, but also the “From” field?



I have been wanting this for ages and wished Thunderbird would eventually implement it..little did i know it had this all along, right from version 0.5…Thank you thank you thank you for writing this article to share with the world :)

Richard C Haven

Yes, I know this thread started a year ago, but Google likes it, so why not me.

Identities are great until you have more than five of them. Thunderbird must improve the UI for managing these things and perhaps sort them alphabetically (by name OR email Reply-To) so I can find which one I want when I am sending mail (replying does nicely default to using the original To: address).

Who is the best person to hear my plea ?


Thanks for the idea, I’d never even thought about it before. I use a Gmail account for my main one though, and even though I set up the Identity properly (I think!) when I send test emails out to my other accounts, it still shows up as being from my gmail account instead of from my dummy address that i put in. I know that something must be working though, because the dummy name I used as the “FROM” in the identity did show up…just not my dummy email address!

Any ideas? Did I do something wrong? I also have an AIM account I could use the SMTP server for, but I tested it identically and it didn’t work…


Norman, do you know if you can create a dedicated shortcut in Mac OS X.5?


Can anyone tell me about different email folders/addresses/preferences? My wife has one email address; I have another. I have Thunderbird installed once on the PC. What’s the best way of keeping the two instances of our emails separate without installing Thunderbird twice, so to speak? In Eudora, it allowed me to point to the one exe file with her settings (and thus her emails and prefs) and one for mine


I may be too dumb to be here in the first place, but hopefully I’m just a computer and e-mail novice. But I’m confused…

…I have an email account with AOL, free, left over after I dropped AOL as my ISP. I have 5 different AOL screenames (multiple identies?) As I see it, I think that I therefore have only one AOL email “account”, but with 5 identities/screenames. Is this a situation where Thunderbird’s “Multiple Identities” should work? My tinkering does not seem to get the multiple screenames to work. (I suspect this is not a case of true Multiple Identities in the sense Thunderbird intends, because among other reasons I never have any trouble sending and receiving emails under the separate screen names.

Thanks for your patience. (I supect…duhhh..that this is not even an appropriate place to post a query and expect an answer. I’m learning :\

Peter B

Multiple identities are great!

(And of course they’ve been present since the beginning of time, even in the good old console pine)

But Thunderbird 2.0 screwed them up a bit, at least for those, who used it before. (tb 1.5). In 1.5 you could only set the name and address of the identity, but not outgoing SMTP, sent-mail saving folders, etc. But in 2.0 you can set them (which is good), but not only can set them, but HAVE TO set them. There is no “use default” option. So if you have an account with many identities, and want to change the outgoing SMTP for a specific incoming account, then you have to do that for ALL of the identities, which is insane, imho. Hope, they’ll fix it for next release :)


I just started forwarding my fastmail emails to a different address. This helps immensely! Thank you!

Judi Sohn

Valor, not quite. has multiple accounts, not multiple identities that can be tied to a single account as I’m talking about here. Yes, you can put in multiple email addresses and select which one to use when replying, but it’s still a manual process when you’re replying to select the right one, and you can’t automatically have the message use a different SMTP server or file to a different location based on that choice.

In general, picks a profile based on the *account* that receives the email, not the email address. So if you have and email coming in to the account you have identified as, your reply (assuming you forget to change it manually) will always appear to be from even if the incoming email is addressed to support@ and was forwarded to the mary@ mailbox by the mail host.

Worse, (at least in a previous version, not sure about the Tiger version) will “forget” the account that received the email if it was sent to a local folder by a filter. So *all* replies will be from the default account, regardless of the account that actually received the email. Sure, you can change it manually on each email, but who wants to do that?


Umm, has done this since the beginning of time.. is this really a new feature for the rest of the world?


Thank you. I have been using a “collection” IMAP account and sending email thru individual SMTP servers. Using Outlook, the incorrect “from” would occasionally slip out. Thunderbird will help. The automatic BCC is also welcome, Outlook lacks that basic feature.


You can also choose a different SMTP server for each identity (see 2nd screenshot).

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