Using Thunderbird for “Send Only” Email

Exactly 10 years ago today, I wrote Use Mailsmith to create a “send-only” email account for TUAW (which was later ‘replaced’ by Engadget).

Unfortunately, Mailsmith did not make the 64-bit transition, and another app known as “Let.ter” seems to have disappeared (although last time I checked, it did still work, but I don’t think it integrated with the macOS address book).

If you use Gmail (or “Google Suite” or whatever it is called), you can use a link like this to send email without ever seeing your Inbox:

Obviously replace with your actual email address. That link will bring up a ‘Compose’ window, which you can use as normal, and then when you send the email, you will be left with a Gmail window which is basically inert.

However, I wanted a Mac app for this. More specifically, I wanted an app which would be able to autocomplete from my macOS Contacts..

It turns out to be much harder than you might think.

Most email apps think they are doing exactly what users want by making sure that they retrieve email as effortlessly as possible. Let’s be honest, that’s a reasonable assumption.

My first attempt was to set up an email app that I don’t usually use, and then either change or delete the IMAP information, so that the app could not download email.

Most email apps will freak out if you do this. First off, most of them won’t even let you delete the IMAP information, and if it is incorrect, they will continually throw error messages as you. Again, it’s a reasonable assumption that users will want to download email, so I can’t really fault them for this, but I found that it was extremely frustrating to deal with the error messages.

Recently, I decided to try this again, and found that it was actually possible to do. It’s not 100% as “clean” as I would like, but it works well enough, and until I find something better, this is what I will be using.

Thunderbird Swoops In

Thunderbird is the mail app from Mozilla, the people who make the Firefox web browser. I had tried this a few years ago and couldn’t get it to work, but it struck me as the email app that was most likely to allow this level of customization.

A search for “Thunderbird Send Only” led me to this post on Superuser:

A Thunderbird account is only for receiving mail. It cannot send mail at all.

To send mail in Thunderbird, you use an identity, not an account. Unfortunately, Thunderbird’s user interface makes the relationship between accounts and identities confusing, as the “Manage Identities” button is found within Account Settings.

Add an identity to your default account, and if necessary add a separate SMTP server for the new identity, but don’t otherwise configure the account. The new identity can send mail independently of the account, and it will never try to receive mail.

I also came across forum post from January 3rd, 2009 (!) saying essentially the same thing, so I decided to give it at shot. Apparently this has been possible for a lot longer than I realized.

The Thunderbird distinction between Identity and Account is important, so I will try to use both terms very carefully from here on.

Here’s the Downside

As far as I can tell, in order to set this up, you have to give Thunderbird access to a “real” email account to create the Account.

You can set this account to not download email automatically at launch, and not to download email periodically, but if you click on the ‘Inbox’ it will download email in the inbox, so that makes it a “No Go” as far as being a 100% reliable “send only” account for that email account.

However, I have an old Gmail account which I pretty much never use, which gets almost no email (even spam!). I created it for a project or something which never went anywhere. So it’s a good Gmail account to use to set up the Thunderbird account because even if it did download email, and even if there was email for it to download, there would be nothing in there to distract me.

You could even set up a new Gmail account and create a Gmail filter to automatically delete all incoming email. But I had this one already, so I decided to use it.

If you don’t have a spare email account, creating a new Gmail account is a bit of a hassle, but, IMO, worth it.

Here’s How to Do It

Step 1: Set up a new account in Thunderbird using an existing email account. This is not the email address you want to use for “Send Only” but another “dummy” account.

Step 2: Once you have it setup, click on the very top level (see screenshot above, item #1), and then choose “Account Settings” (item #2).

Thunderbird 001 Click On Account Settings

Step 3: Click on “Manage Identities” at the bottom right corner.

Thunderbird 002 Manage Identities

Step 4: Click to Add a New Identity

Thunderbird 003 Identities Add

Step 5: Fill Out Information. Items 5, 6, 7, and 8 are the only ones that are required (as far as I can tell.) #8 may not be required, but it’s definitely something I recommend. This should be the account you want to use as “Send Only”.

Thunderbird 004 Fill Out Identity

Don’t click “OK” yet – click on #7 to create a new SMTP server. This is a vital step!

Step 6: Enter SMTP Server Information. This is the information for the “Send Only” account.

Thunderbird 005 STMP Info

Note that I have given the “Description” (item #9) to make it obvious that this is the SMTP server I want to use when using it as “Send Only”.

Items 10-14 will differ, depending on the options for “Connection Security” and “Authentication Method” that you will have to choose for your email provider. What is shown here is for Gmail, but if you use another email provider, it may be different. (If email does not send, or does not send from the proper account, remember this step, because this is probably where you will need to come back to.)

Step 7: Set Default Identity.

Click the “Manage Identities” button again (see Step 3) and you should have two Identities now. Either choose the one you want to use as “Send Only” and click “Set Default” or click the one you aren’t going to use and click “Delete”.

Thunderbird 007 Default Identity

You can see above that I’ve already deleted the one I’m not planning to use.

Step 8: Set the Outgoing Server (SMTP).

Thunderbird 006 Default STMP Server

Click the next to #15 and change it to the “Send Only SMTP Server” that we created in Step #6. I wish I could delete the other SMTP server, but I cannot find a way to do that. Let me know if I missed it.

Step 8: Send a Test Message.

  • Close the “Tab” with the account settings.
  • ⌘N to open a new “Compose” window.
  • Check the “From” address is the correct one (if not, go back to Step 7).
  • Send a test email to yourself. If you set up a Gmail SMTP server, the first time you send a message Thunderbird will open a browser window to authenticate you with your Gmail account. Once you’ve done that once, you won’t need to do it again.

There Is No Step 9. Hopefully.

I hope that will work for you. If not, let me know. It can be a bit of a challenge writing up instructions after the fact because I’m always afraid I will forget some detail or some step that I did the first time through.

If you want to discuss this, please post to this thread on the Mac Power Users forum.

Optional Steps

  • in “Account Settings” click on “Server Settings” and uncheck the boxes next to “Check for new messages at startup” and “Check for new messages every X minutes” and “Allow immediate server notifications when new messages arrive.” This should prevent Thunderbird from automatically downloading email from your the email account we setup in Step 1.
  • in “Account Settings” click on “Copies & Folders” and choose options for where you want copies of sent messages to be stored. You may want to set it up to automatically BCC yourself at the “Send Only” account so you’ll have a record of those emails in that account. (Note: if you use Gmail for SMTP, it will automatically store the message in your Sent email ‘folder’ on Gmail, so you don’t need to do that for Gmail.)

Listen, record, and even pause Live using VLC and Audio Hijack has a schedule of live shows which you can listen to as they are recording. Most people just listen to these in a web browser, because that makes the most sense and is the easiest way to do it. If you have an iOS device you can use the free app which I will also use if I am not at home when a show is live.

However, if I am on my Mac when a show is live, I prefer to listen using VLC which is a free app, and I also like to record the live show, either so I can pause it if I get interrupted or can just listen later to the MP3. This is accomplished by using VLC plus Rogue Amoeba’s Audio Hijack program, which is not free, but which any self-respecting Mac nerd ought to own because it’s amazing cool and powerful. It can do 1,000 more things than this, but I’m just going to talk about this for now.

Using VLC to listen to live

To listen to in VLC, you need the URL to the live-stream server:

That URL is only enabled when the live-stream is active.

First go the File » Open Network:

VLC: File » Open Network

Second, put the URL into the Network URL in the Open Source window that will open:

VLC: Network Pane

If the live-stream is active, it will look like this:

VLC: Live Stream window

If you’re comfortable with the command line, you can replace the first two steps by this line in Terminal:

open -a VLC ''

which will automatically open VLC with the stream playing (again, only if it is live).

Record Live with VLC and Audio Hijack

If you want to record with Audio Hijack, we can still use VLC, and then set it up the output to go two places:

  1. To an MP3 so we can listen later

  2. To the Mac’s speakers

In number 2, we also add a “Time Shift” block, which will allow us to pause the livestream (which will keep recording in real-time to the MP3, because that is completely separate). It will also allow us to rewind the broadcast if we missed something. It’s sort of like TiVo for audio.

The setup (which Audio Hijack calls a “Session”) will look something like this:

VLC in Audio Hijack

You can see there are two “branches” from VLC, one going up to an MP3, and the other going down to “Time Shift” and “Output Device”.

We have to tell VLC what to play when this Session runs, which we can set by clicking on the VLC “block” in Audio Hijack, which will reveal the VLC settings. You can see it here:

VLC settings in Audio Hijack

Note that the box next to “Open URL” is checked, and the URL is entered into the appropriate box.

You can also change the MP3 settings (not shown) by clicking on the “Recorder” block. I have mine set to save recordings to the folder ~/Music/Audio Hijack/ with filenames that are formatted like this:


The first part makes sure that all the recordings will be grouped together by name, and then the date (YYYY-MM-DD) followed by the time that the recording began (13-04 refers to 1:04 p.m. local time on May 16th of 2019).

You can download my Audio Hijack session file here: Relay-to-Speakers-and-mp3.ahsession

Assuming you have Audio Hijack installed, you should be able to double-click on the Relay-to-Speakers-and-mp3.ahsession file and have it open right in Audio Hijack. You can then adjust any of the settings that you might want to change. (The file also assumes that VLC is installed at /Applications/

p.s. – You can easily adapt these instructions to record other podcasts which record live, by creating a new “Session” in Audio Hijack and changing the URL of the live-stream server. For example, ATP’s URL is

With ATP, you can even use Audio Hijack’s “Schedule” feature to record Wednesday nights at 8:58 p.m. (US/Eastern) to 11:55 p.m. and automatically record most of ATP’s live shows. They do occasionally change that date/time of recording, but that will catch most weeks. I suggest starting a few minutes before 9:00 p.m. not because I want to subject you to Marco’s Phish concerts, but just to give yourself a little leeway. Also, they usually stop recording long before 11:55 p.m., but Audio Hijack is smart enough to figure out when there is no sound playing.

Trying to make a Virtual Machine from Apple’s recent DMG releases of Mac OS X

Scroll down to “Update and Solution” to see how to get this to work.

Apple recently released new installers for Mac OS X/OS X/mac OS to deal with expired certificates:

If an installer says it can’t be verified or was signed with a certificate that has expired – Apple Support

Three of the six are links to the Mac App Store:

The other three are URLs to download DMGs:

Today I tried (and failed) to create a new Virtual Machine in either Parallels or VMware Fusion using one of these DMGs, specifically, the El Capitan one.

I will explain what I did, and where I got stuck, in the hopes that someone else might figure out what I did wrong and point me in the right direction.

Download the DMG

Apple has created three DMGs for Yosemite, El Capitan, and Sierra, but couldn’t be bothered to give them useful names, so Yosemite and El Capitan are called ‘InstallMacOSX.dmg’ and Sierra is ‘InstallOS.dmg’.

Likewise the DMGs aren’t named usefully when you mount them either, so make sure you name the DMGs well when you download them to avoid confusion. Here’s how to download it and rename it at the same time

curl --fail --location --continue-at - --output "$HOME/Downloads/InstallElCapitan.dmg" \

Mount the DMG

Open the ‘~/Downloads/InstallElCapitan.dmg’

That will leave you with

“/Volumes/Install OS X/InstallMacOSX.pkg”

Extract the App

Don’t try to install from that .pkg file, it probably won’t work unless the Mac you’re using is capable of running El Capitan:

Instead, open it with Suspicious Package which will let you examine the contents of the .pkg file, as shown here:

Note the area in the red box. Obviously that’s not the full installer, despite the .dmg being over 6 GB. But let’s export it anyway:

Save it to /Applications/ (or wherever you prefer, but that’s where I’ll assume it is for the rest of these instructions).

Don’t eject “/Volumes/Install OS X/InstallMacOSX.pkg” yet, we still need to get the actual .dmg from it.

Get the other DMG

Download The Archive Browser if you don’t already have it (it’s free!) and use it to open “/Volumes/Install OS X/InstallMacOSX.pkg”.

It will look like this:

Click on the triangle to the left of “InstallMaxOSX.pkg” to reveal its contents, and select the “InstallESD.dmg” file from it.

Once it is selected, choose “Extract Selected” from the bottom-left. Save it to ~/Downloads/ (it won’t be staying there long).

Ok, this part could be confusing…

When The Archive Browser exports the file, it will not just export the “InstallESD.dmg” file. First it creates a folder “InstallMacOSX” and then it created “InstallMacOSX.pkg” inside that folder, and the “InstallESD.dmg” file is put inside the .pkg… but you can’t see it, because the .pkg file won’t let you open it.

That’s OK, because we’re going to use to move the file into place anyway.

First we need to create a directory inside the ‘Install OS X El’ which we previously saved to /Applications/. We’re going to use the same folder for two commands and we want to make sure we get it exactly right both times, so we’ll make it a variable:

DIR='/Applications/Install OS X El'

Then use the variable with mkdir to create the folder:

mkdir -p "$DIR"

and then we need to move the “InstallESD.dmg” file into that folder

mv -vn "$HOME/Downloads/InstallMacOSX/InstallMacOSX.pkg/InstallESD.dmg" "$DIR"

Note: you probably want to trash the ‘~/Downloads/InstallMacOSX/InstallMacOSX.pkg’ (and its parent folder) now that it is empty, to avoid confusion later

mv -vn "$HOME/Downloads/InstallMacOSX/" "$HOME/.Trash/"

Now if you look at the ‘Install OS X El’ in the Finder, it should show itself as 6.21 GB:

open -R  '/Applications/Install OS X El'

So close, and yet…

VMWare was willing to start trying to make a virtual machine using the app, but it failed when it came to the actual installation part:

I don’t know what to try next. Parallels would not use either the ‘Install OS X El’ or the ‘InstallESD.dmg’ to try to create a new virtual machine.

Update and Solution

I posted a question on the VMware Fusion support forum asking how to do this, and someone came up with a very clever solution, which I will replicate here in case others are interested. The idea is simple, but I never would have thought of it.

  1. Create a virtual machine of any version of macOS, even the current version that you are using on your Mac.

  2. Inside the VM, download the .dmg (see below) and mount it.

  3. Launch the .pkg inside the .dmg.

  4. The .pkg seems to understand that it is inside a VM, and will install the app, which it would not do outside of the VM. Note that the says that it will only take a few megabytes, but that is incorrect.

  5. Find the “Install OS X El” (or whatever the app name is) in the /Applications/ folder inside the VM. It should be over 6 GB in size.

  6. Copy the “Install….app” from the VM out to your actual Mac.

  7. Create a new VM using the “Install….app” from the /Applications/ folder on your Mac.

Step #4 is the part that I never would have guessed. The .pkg would not install the app outside of a VM, but will install it inside of a VM.

This worked perfectly with the El Capitan .dmg file, and I’m currently doing the same with Yosemite and Sierra. Then I’ll try the older versions of Mac OS X from old installers that I have from before they disappeared from Apple’s servers.

Update 2

Turns out that Rich Trouton wrote about this technique back in early 2017:

Downloading older OS installers on incompatible hardware using VMs | Der Flounder

But I wasn’t working with VMs at the time, so I must not not stored that in my long-term memory.

Update 3

I had saved the older installers for Lion, Mountain Lion, and Mavericks, which are no longer available for download.

Each of them still installed as a VM. Apparently they were not signed with the certificates that expired.

Older versions of Mac OS X (10.6.8 and before) are not available to virtualize.