On 2009/01/07 11:48, Richard Koett wrote: > 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:
Oh, I had to guess a bit because the full information wasn't there - full headers and log entries might help explain things.. > 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 ---
