Stuart Henderson wrote: > Ok, most likely scenario: spammer sends to solom...@myramstore.com, > hits Sendmail, Sendmail tries to pass it to Exchange.
Thanks again for taking time to help. Just to clarify, however, my sendmail box is not an MX server for myramstore.com. Perhaps what's happening is: 1. Someone sends spam to my domain from solom...@myramstore.com 2. Although it is not the preferred MX server for my domain, my sendmail box receives the spam first 3. My sendmail tries to bounce the spam back to solom...@myramstore.com for some reason (perhaps a non-existent addressee) 4. The MX server for myramstore.com responds that solomany is not a valid user and tries to bounce my bounce back to mailer-dae...@cybernet.ca 5. This double-bounce is sent to the Exchange server because it's the preferred MX server for cybernet.ca 6. Exchange doesn't recognize MAILER-DAEMON as a valid user. The above scenario seems plausible to me, but it doesn't explain why Exchange appears to have been asked to delivery something to solom...@myramstore.com. > Exchange generates a bounce *by email* to the sender > address (most Exchange versions don't reject "user unknown" > at the SMTP port, instead they fully bounce the email. oops.) > > I guess you are also relaying outbound mail via the sendmail > box so Exchange sends it there, Sendmail tries to deliver it > and fails, then as you're receiving postmaster's mail you get > a copy of the "double bounce". > > If that is what's happening, the fix is to reject mail for > invalid users before the message hits Sendmail. You can create > /etc/mail/access populated with a list of the valid addresses > on the Exchange server, something like: > > To:myramstore.com error:550 5.1.1 No such user > validu...@myramstore.com OK > anot...@myramstore.com OK > etc. > > Then rebuild the hash file as shown in the comments. I'm actually using virtusertable to relay mail to specific users, and include lines like this after the list of accepted names for each domain: @cybernet.ca error:nouser User unknown I'm not sure if this is rejecting invalid users "before the message hits sendmail", however. It seems to me that I need to do several things: 1. Disable sending bounce messages to non-local users in Exchange (I seem to recall doing this previously but will double-check) 2. Disable sending bounce messages from sendmail to domains it's not an MX server for. (I'll have to look into how to do this). 3. Make MAILER-DAEMON a valid alias on Exchange for when messages hit MX servers out of order Any other thoughts or suggestions? Richard Koett. >> --- BEGIN SAMPLE --- >> Delivery has failed to these recipients or distribution lists: >> >> solom...@myramstore.com >> The recipient's e-mail address was not found in the recipient's >> e-mail system. Microsoft Exchange will not try to redeliver this >> message for you. Please check the e-mail address and try resending >> this message, or provide the following diagnostic text to your >> system administrator. >> >> The following organization rejected your message: >> sitemail.everyone.net. >> >> Diagnostic information for administrators: >> >> Generating server: mail.cybernet.ca >> >> solom...@myramstore.com >> sitemail.everyone.net #<sitemail.everyone.net #5.1.1 SMTP; >> 550 Recipient Rejected: No account by that name here> #SMTP# >> >> Original message headers: >> >> Return-Path: <MAILER-DAEMON> >> Received: from localhost (localhost) >> by mail.cybernet.ca (8.13.4/8.13.4) id n06HNI36007149; >> Tue, 6 Jan 2009 09:23:18 -0800 (PST) >> Date: Tue, 6 Jan 2009 09:23:18 -0800 >> From: Mail Delivery Subsystem <MAILER-DAEMON> >> Message-ID: <200901061723.n06hni36007...@mail.cybernet.ca> >> To: <solom...@myramstore.com> >> MIME-Version: 1.0 >> Content-Type: text/plain >> Subject: Returned mail: see transcript for details >> Auto-Submitted: auto-generated (failure) >> --- END SAMPLE ---
