> How can I deny all MAIL FROM: <> commands from hosts which > are not MX for a domain?
You need to provide more information about the environment you're working with. If you're running MS-Exchange on MS-Windows, I don't think there's a mechanism available to do this type of checking. However, if you're in a UNIX environment of some type, depending on your mailer, you can pass incoming messages through a script that could parse and validate the mail server name and IP address. What you're likely to find, however, is that this isn't a workable solution in the real world. For example, a large company with many locations will likely have a mail server at each location, and each server will likely be configured to forward outgoing e-mail directly to the recipient (this is the most efficient and reliable method). However, incoming mail is likely to be forced through one or two "advertised" MX systems for the domain, where it can get checked for viruses and then re-routed to the proper internal mailbox server for the specified user. So it's very likely that valid e-mail from real mail servers would be blocked. The other problem you'll run into, as we have here using MS-Exchange, is that some domains don't setup PTR zones for reverse (IP to name) lookups. In order to verify the incoming machine name you have to take its IP address and perform a reverse DNS lookup. Then you can parse this into hostname and domain name, and determine whether you want to reject mail from the domain (as we tried with MS-Exchange), or run a script to identify the MX's and attempt to match the server IP to the MX IP. This will all fail if there are no PTR zones setup for the server. It is also very likely that, when PTR zones exist, they contain only dummy information to avoid possibly giving away information that might be beneficial to an intruder. So, while this would be an interesting programming exercise, I don't think it will achieve the intended results without some significant problems (i.e., potential lost mail from important customers). ______________________________________________________________________ Mark A. Medici | DBM Associates -=]#[=- Computer Sales and Services Sr. Systems Eng.| One Salem Square #104W, Whitehouse Station, NJ 08889 [EMAIL PROTECTED] | Phone: 908-534-1665 Fax: 908-534-1244 www.dbma.com > -----Original Message----- > From: Octavio / Super [mailto:[EMAIL PROTECTED]] > Sent: Friday, January 04, 2002 5:41 PM > To: [EMAIL PROTECTED] > Subject: MAIL FROM: <> > > > Hello! > > How can I deny all MAIL FROM: <> commands from hosts which > are not MX for a domain? > > Thanks, Octavio. > >
