Hi Folks. I use sendmail as the MTA for our company. Lately employees have started working from home. These home users send their email through our company MTA using SASL-AUTH. This works fine for the most part but lately we've seen problems with this. The SORBS blacklist looks not only at the IP address of our company's MTA but also at the IP address of our employees home computers. (After all, the home computer IP address is revealed in the mail header.)

SORBS has been rejecting emails sent from our home users because their dynamic IP address is present in the email headers. This is true despite their email passing through our company MTA which is on a properly forward and reverse mapped static IP.

The company MTA is not listed in SORBS but the mere presence of a dynamic IP somewhere in the mail header is causing outright rejection. This seems bizarre to me considering home workers sending through a company relay is a common and reasonable business practice.

Can sendmail offer a solution here? For example, to change headers to obscure the IP address of the MUA or make the email appear to have originated directly on the MTA? I don't want to mess with internet RFC but frankly I'm out of ideas for how to get the mail delivered.

Feel free to request more information or supporting evidence.

Thank you in advance for your insights!

With further research I've seen that a milter can be used to modify or remove the Received header containing the dynamic IP. This is not something I want to do. This breaks RFC 2821. I would much prefer just some advice on how to cope with the dynamic-ip scanning behavior of SORBS (as outlined earlier in my last post). I will go post a message specifically about SORBS and strategies for coping with it in a different forum if no advice is found here. Thanks again.