Re: smpt relaying
- From: Garen Erdoisa <gerdoisa@xxxxxxxxxxxx>
- Date: Tue, 25 Jul 2006 16:41:36 -0600
D-42 wrote:
Hi,
This is my first time posting here, and I hope I'm in the right place.
I'm running a private mailserver for my small company and its working fine. But I've got 2 concerns/questions.
First, it receives mail no problem, and while I do have a "static" ip address and am "allowed" to run servers, its still served by telus' DHCP and is on a number of "dynamic black lists" So I have it set up to relay outgoing mail originating on the LAN through the ISPs mail server. Are there any issues with this configuration that I should be aware of? Does it violate any rules, standards, or rfcs?
Second, while it seems to be working, I recently got a few bounces and I'm not entirely sure why, the message is as follows:
Final-Recipient: RFC822; <name-supressed@xxxxxxxxxxxxx>
Action: failed
Status: 5.1.8
Remote-MTA: dns; mx2.prserv.net (12.154.55.40)
Diagnostic-Code: smtp; 556-204.209.205.55 blocked by mx.rbl
556 RBL block by MX.RBL - Bad Domain (20060722)
As a "guess", based on the wording of the diagnostic code, the server administrator of the receiving server has either a private DNS blocklist they are using, or has setup a manual access list entry, or has a sendmail filter (milter) program running that compares the incoming domain stamped on the envelope sender or the From: header vs the domain that owns the connecting IP. If they mismatch, then their mail filter rejects the mail. That is what SPF does, but usually an SPF reject will say that the failure was due SPF. Without more specific information and knowledge of how the receiving server is setup guessing is about all anyone on the outside can do.
So, unfortunately in this case, the diagnostic code given will only have meaning to the administrator of the system that is generating the bounce. No one else on the outside will be able to decipher it beyond knowing that the mail was rejected for "some" reason.
-----------
The 204.209.205.55 address is the ISPs smtp server it got relayed through. (telus)
But I can't find anything about MX.RBL, who runs that list, or what "Bad Domain" means.
IMO (as a guess) that is most likely a private blocklist. Because of that you are unlikely to find any publicly available information on it.
I don't even know if its an issue with my domain/my mailserver? or is the telus mail server for whatever reason been blacklisted by someone?
Any suggestions or insight would be appreciated!
You could try using your account on telus? to try to mail the administrator of the problem system and ask if s/he can punch a hole through their blocks for you. I suspect that if the system sees the domain in the From: header match with the owner of the MX, then it would be accepted. That's more likely to happen if it's one of their customers that makes the request rather than someone on the outside.
Otherwise, you are probably out of luck.
As a side note, presuming you haven't done so already, you might want to setup SPF records for your domain such that they show telus's mail servers as authorized output mail servers for your domain.
--
Garen
.
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