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I'm using:

thunderbird-10.0.3-1.el6_2.x86_64 on Scientific Linux 6.1

and if I send an e-mail (with Gmail) from my Thunderbird then I can see that the e-mail I sent contains a very-very bad thing: 

Received: from [192.168.1.142] (31-149-121-34.pool.myisp.com. [31.149.121.34])

So ALL the e-mail that I'm sending containst my NATed IP address + my public IP address.

Can I delete/remove these lines, so that they will be aren't in ALL the e-mails that I send??

UPDATE: if I send an e-mail with the gmail web interface, then: 

Received: by 10.112.129.10 with HTTP; Sat, 14 Apr 2012 09:20:13 -0700 (PDT)

Aren't there any Thunderbird Add-ons that modifies my IP Address in the e-mail?

Gilles 'SO- stop being evil'
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LanceBaynes
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  • [Semi-helpful Google Support site on this issue,](http://support.google.com/mail/bin/answer.py?hl=en&answer=26903) but in general I don't see much reason for concern. If your IP address were sensitive information, you probably wouldn't use GMail anyway. – sr_ Apr 14 '12 at 14:50
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    That line is not added by thunderbird, but by the first smtp server you deliver your message to, as it received the message from your computer. Just open the message and look for all the `Received:` headers: they show the trail of where did the message pass through. That's how email works. Your only chance is convincing the mail server not to disclose your IP (I guess this may be difficult), or use some anonymization service. Of course stuff sent through a web interface won't have your IP address under `Received`, because it does not originate from your computer, but from the web server. – njsg Dec 12 '12 at 06:58

2 Answers2

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You cannot hide your public IP address (assigned to the WAN interface of your router). You can, however, hide your private IP address (assigned to the NIC of your computer):

  1. Go to Thunderbird's about:config page (in version 3.1 it's Edit > Preferences > Advanced > General > Config Editor).

  2. Find the mail.smtpserver.default.hello_argument preference (if it doesn't exist create it by right-clicking > New > String).

  3. Enter "localhost" (or some other string) as its value.

UPDATE (to answer your update): Mail messages sent via web interfaces (like Gmail's, Hotmail's etc) can have an X-Originating-IP header that shows your public IP. Some services add this header (e.g. Hotmail) and some don't (e.g. Gmail).

Baldrick
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As far as I know there is no way to do this with Gmail. The only way to hide your client IP is by setting up your own mailserver and tell it to discard or modify prior Received-headers.

Generally people are not even aware that an email contains headers, let alone being able to view it from their client. There should be no reason for hiding this information.

Frank
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  • Even then, won't the address of said mail server be included by further mail servers when they receive the message? As far as you manage to keep information away from the WHOIS database or the like, it should be less problematic, of course. – njsg Dec 12 '12 at 07:00
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    @njsg are you kidding? There are many reasons to hide your IP. Pseudonyms, whistle blowing (can't prove you sent the emails), privacy in general. People don't need to know where you are. That's just creepy. – KI4JGT Nov 15 '13 at 23:59