Our Mail Server, which also runs the SMTP task, is seated behind a firewall and sends out mails directly to the Internet. The firewall permits SMTP connections both in-bound and out-bound.
The problem is when the e-mail is sent out to the recipient. You can actually see the IP address of our Mail Server that is behind the firewall. The recipient can also see the external interface IP address of the firewall.
Can the IP address of the Mail Server be removed?
These IP addresses are part of the standard email header information that shows the route that an email takes. However, this should not be a problem for you since you have a firewall. You should assume that a potential attacker knows your IP address and protect yourself accordingly. You have done so.
This was first published in May 2001