Re: Sendmail and Available STMP Services?
- From: Grant Taylor <gtaylor@xxxxxxxxxxxxxxxxx>
- Date: Fri, 06 Mar 2009 15:58:53 -0600
On 03/06/09 15:24, spamfree@xxxxxxxxxxx wrote:
I have cut some of the text from previous postings that I did not think was germane to my replies but if you think otherwise, my apologies and please feel put any text back you want.
Not a problem at all. I simply wish that people would cut their reply messages down to what they and the person they are replying to sent as opposed to the entire back and forth conversation.
I am not sure why they would do this other than to be mean spirited, but I for sure don't know everything.
I'm not sure they would do it to be mean spirited per say. I was thinking more along the lines of the ISP installing an SPF filter to help reduce the amount of spam coming in to their subscribers (mailboxes). In the process the same filter would now potentially see email coming from your subscriber IP, but still being passed through their SPF filter which should honor your SPF record. In this case, your ISP's SPF filter would have to recognize your IP as a valid IP for your domain.
I guess that is what I am asking for but it would have to use the domain name in the decision making if the service was forwarding for more than one domain using the same receiving IP address.
*nod*
There is not a way (that I know of) to do TCP port forwarding /and/ standard mail relaying on the same IP and port pair because of the complexities of TCP and SMTP. It will need to be one or the other.
Right here you lost me. Why couldn't it forward ALL mail and let my server determine which queue to put the mail in based on the "To" address? What technical reason would require the forwarding server to make those decisions?
The relay (forwarding server) /can/ blindly queue messages for delivery to your server. The problem is that relay server will be responsible for sending bounces to invalid recipients when your server rejects messages based on the recipient. Thus the relay server is now participating in a Joe Job and sending back scatter spam. To prevent this problem the relay server needs to know (at the very least) valid recipients on your server so that it does not accept messages to relay that are for invalid recipients.
Perhaps back scatter would be a non technical one, but I do not have very much email that falls in that category other than the dsnbl email which as you say, would probably not work.
Correct. The list of valid recipients on the relay is all about preventing as much back scatter as possible.
I am sure that could be done on my server but I am not sure I would want to unless it was a requirement. I have a throw away email account on a free web based mail server that I use for testing that works that way. I can send an email to a non existent user on my server from that account and I never receive a return mail indicating that delivery could not be made. That is just plain rude.
I agree with you completely. However relaying email has become a precarious position. The problem is that when your receiving server rejects messages, now the relay is responsible for sending DSNs and we are back to the back scatter issue.
This problem might be mitigated if collectively you and your relay take steps together so that the relay does as much filtering for you as possible, thus reducing the likely hood that you will reject a message from the relay.
Interesting thought. That would certainly make forwarding all domain mail easier.
*nod*
Keep in mind that in reality this is not a forward / relay per say, rather an extension (port forward) of your own server.
My first reaction was you were wrong on that score. I looked at one of my log entries (below) and as they do most times it shows the dsnbl blocked a dynamic IP address. Based on that I figured it was blocking a PC sending through a server. On closer inspection however I see the same IP address in the "relay=" field which I would assume means it came direct so you are right.
;)
I guess that means not all ISPs are blocking port 25 outbound. I would think by now that would be a given.
I have two knee jerk reactions:
- Hardly!
- I wish!
Then you start getting in to other issues that are in and of them selfs a good discussion, but completely off topic. (Fell free to start a thread if you want to.)
Mar 4 13:51:45 myserver sm-mta[28598]: ruleset=check_relay, arg1=114-45-140-150.dynamic.hinet.net, arg2=127.0.0.11, relay=114-45-140-150.dynamic.hinet.net [114.45.140.150], reject=550 5.7.1 Rejected: 114.45.140.150 listed at zen.spamhaus.org
Yep. 114.45.140.150 was sending directly to your server. Your server queried Zen SpamHaus and found 114.45.140.150 to be black listed and thus rejected the message being sent to you.
Thanks, I will keep that in mind, but I am really hoping that after the transition this will turn out to be much ado about nothing (sigh).
You are welcome. And it never hurts to be prepared. At the worst, it was an exercise (in what I will not say) and at best every body learns something. :)
Grant. . . .
.
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- Sendmail and Available STMP Services?
- From: spamfree
- Re: Sendmail and Available STMP Services?
- From: Grant Taylor
- Re: Sendmail and Available STMP Services?
- From: spamfree
- Re: Sendmail and Available STMP Services?
- From: Grant Taylor
- Re: Sendmail and Available STMP Services?
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- From: Grant Taylor
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