Hide the user agent when sending emails with Thunderbird
Thunderbird, and other mail clients as well, include information in each email you sent that reveal information about your operating system, the mail program and the version of it that you are using. While that is certainly not an issue if you are sending an email to your mum, close friends or other contacts you know, you are better of not to reveal what you are using to someone that you do not trust or know.
The reason for this is simple: The operating system and mail client can provide malicious users with information that they can use to attack your system. Say they notice that you are running an older version of Thunderbird or another email client with known vulnerabilities. They can then use the information to attack your system efficiently thanks to those information that you have provided them with.
You can check the user agent in Thunderbird by either enabling full headers under View > Headers > All, or by clicking on Other Actions > View Source.
The user agent on the screenshot above reveals the operating system, Windows 7 64-bit, the email client and the version of that client.
There is unfortunately no switch in the program's settings to change the user agent in Thunderbird. What you need to do is add a hidden parameter to the advanced configuration to do that. Here is how this is done.
Open the settings of the email program with a click on Tools > Options. Switch to the Advanced tab here and click on Config Editor under General. You may see a warning message if that is your first time opening the about:config window. If that is the case click on I'll be careful to continue.
Right-click in the parameter window and select New > String from the options. Enter general.useragent.override in the first form that pops up, and nothing in the second. This sets the user agent to a blank and that is what recipients see when they analyze the email header.
It is unfortunately not that easy to remove the preference again. For that you need to edit the prefs.js file in your Thunderbird profile. You should find it under Windows 7 in the C:\Users\username\AppData\Roaming\Thunderbird\Profiles\random.default folder. Locate the general.useragent.override line and delete it completely. Make sure Thunderbird is closed when you edit the file.
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You said that Outlook isn’t your main email client, so which is your main one?
I think its thunderbird
It is Mozilla Thunderbird.
Awesome! This actually solved my problem… what a stupid bug.
If this is the same bug that I’ve encountered, there may be another fix: (1) hover over open Outlook item in Taskbar, cursor up to hover over Outlook window item, and right-click; (2) this should give you Restore / Move / Size / Minimize / Maximize — choose Move or Size; (3) use your cursor keys, going arbitrarily N/S/E/W, to try to move or size the Outlook window back into view. Basically, the app behaves as though it were open in a 0x0 window, or at a location that’s offscreen, and this will frequently work to resize and/or move the window. Don’t forget to close while resized/moved, so that Outlook remembers the size/position for next time.
THANK YOU Claude!!! I could get the main window to launch but could not get any other message window to show on the desktop. You are my hero!!!!
Solved my issue! 6 years later and this is still problem…
Fantastic. Thank you. Size did the trick.
This solved my Outlook problem, too. Thank you. :)
Thank you so much, this started happening to me today and was causing big problems. You are a life saver, I hope I can help you in some way some day.
You are a god – thank you!
thanks a lot…. work like charm.. :-)
Yah…thanks Claude. I’ve been having the same problem and tried all the suggestions…your solution was the answer. It had resized itself to a 0/0 box. Cheers
Excellent post. This had me baffled even trying to accurately describe the problem. This fixed it for me.
Thank you
Thanks a lot for the article. Don’t know why it happenend, don’t know how it got fixed, but it was really annoying and now it works :-)
Thanks a lot. I was facing this issue from past 3 week. I tried everything but no resolution. The issue was happening intermittently and mainly when I was changing the display of screen ( as i use 2 monitors). The only option i had was to do system restore. But thanks to you.
I’ve been tried to sole this problem for 12hours. Your comment about changing the display of screen helped me a lot!! Thanks!!
Thank you…don’t know why this happened but your instructions helped me fix it. Running Windows 10 and office pro 2007
Great tip! Thanks!
Worked for me, too – thank you!!!
It’s Worked for me, too
thank you very much!
I had a similar issue with Outlook 2013 on Windows 10 and this helped me to fix it. Thank you very much!
Thank you so much. Solved!
Considering you published this in 2012, incredible not been debugged by Microsoft.
Thank you again. M
This problem was faced by only one user logging to TS 2008 r2 using outlook 2010.The issue was resolved.
Thanks.
Great tip. Thank you!!!! If it helps, I had to use the Control Key and the arrow keys at the same time to bring my window back into view. Worked like a charm.
Thank you, this worked !!!!
Man, you are a fucking god. Thanks a lot, what an annoying bug!!
Awesome, this post solved the issue. Many thanks!