LAN IPs on Mail.app Email Headers

Comments

5 responses to “LAN IPs on Mail.app Email Headers”

1. 

   Luis Silva

   November 16, 2009

   hey Ricardo,

   what’s the big deal? as far as i know, this is normal behavior across most mail clients :o)

   best,
   Luis

2. 

   Odrakir

   November 16, 2009

   Luis, most email clients send your computer’s public WAN IP address, not your private LAN IP.
   Check the mail headers on an email sent by Outlook and you won’t find the PC’s LAN IP. Seems that Thunderbird does the same as Mail.app. Weird…

3. 

   Diogo Gomes

   November 16, 2009

   RTFM

   http://www.faqs.org/rfcs/rfc2821.html

   It’s the IP address of YOUR computer not of the NAT Router.

   And this is very useful if you need to debug from which client behind a NAT the email was sent from 🙂

4. 

   Odrakir

   November 16, 2009

   I never said it was the Router’s IP. :S

   This is useful but it can be used to map your internal network by an attacker.

5. 

   Diogo Gomes

   November 17, 2009

   Just to put things straigh: “…In green my Router’s Public/WAN IP address…”

   It’s true that it might constitute a security threat, and thats why some implementations break the RFC (such as the case of MS Outlook).

   SMTP is one of those way too old protocols, that were years away from thinking about security issues. It is based on best practices, and as such it expects everyone to behave 🙂