Oh look, a Verizon mail server.
Verizon (which uses the bizmailsrvcs.net domain name) runs some very bad filtering on their inbound mail. One thing they do is to test MAIL FROM parameters for legitimacy by seeing if they can get through the RCPT phase of trying to mail to them. The effect of this is that if you are using something that would reject mail from the Verizon test machines, you can't mail anyone using a Verizon mail server.
How exactly do they do this?
As you are in the SMTP transaction they try to run the same sort of test that you and others have quoted in this thread, aiming at the address you claim to be using. If they can get a positive response to RCPT, they'll let your mail in.
This has been discussed here back around the time Verizon started this practice last October, because it is a conceptually a problematic practice and Verizon implemented it badly and first and proceeded to make it worse when they discovered how dumb some other sites were. At this point they have a system that would deadlock if it encountered any other site behaving in the same way.
Unless the Verizon machines are on an RBL that I use, I don't think I'd be rejecting them.
Verizon's machines have historically been open relays. The 'callback verification' has also been seen as abusive by some people, and those machines could be in some blacklists.
For example, I do not accept mail from most of Verizon's network space, specifically including their main outbound machines and there callback mules. For years they had stupid and ineffective relay controls on their mail servers and now they engage in a practice that is completely non-scalable. For all that time that have essentially ignored abuse complaints about any customer who pays them more than $20 a month for access. As far as I am concerned, Verizon offers no mail service compatible with my server.
Plus using bogus domains seemed to get past the block.
Bogus domains or domains that you don't know anything about?
I cannot speak to how Verizon deals with non-resolving domains. I do know that their system has been in flux ever since they deployed it last Fall, and it might be doing different things now than I was last familiar with before giving up the discussion with one of their mail architects.
I know when I get to the bottom of this, and find that once again it isn't really my fault, I'm going to get some grief. So I'd like to fully understand what the situation is so I can go into the "meeting" I'm going to get called into with enough ammo to get myself cleanly off the hook.
I'd crank up the logging on my SIMS server to see more info so I can tell what Verizon is doing back to me, but for some reason it wasn't taking my setting change earlier (no matter what I set it to, it would only log at the Problems level... I'm guessing a reboot will fix it, but the door to the room its in is behind a large pile of computers so I couldn't get to it today.)
Remember that SIMS has discrete log level settings for each module. You probably want the General, Router, and SMTP modules cranked up to Everything to catch the Verizon callbacks.
-- Bill Cole [EMAIL PROTECTED]
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