if mail is rejected send it using antoher SMTP server.

by: egarciatPosted on 2005-03-07 at 16:21:24ID: 13482359

I DO NOT want all messages sent from My outside SMTP server, only those that do not reach it's destination using the blacklisted net.

by: wesly_chenPosted on 2005-03-07 at 16:35:39ID: 13482456

> I set the user SMTP to the other SMTP server outside LAN, the delay will be extremelly high, they don't want that
Hi,

How about use other SMTP server outside the LAN as smart SMTP host? So all your outgoing mail send from your
internal SMTP server to the smart host. And all the incoming emails are forwarded by the smart host to you SMTP server.
So you don't need to change anything on users' side, they still point to your internal SMTP.

This way you can avoid being in blacklist. And also it easy to implement.

Regards,

Wesly

by: egarciatPosted on 2005-03-07 at 16:52:19ID: 13482605

sounds good.. but, how? :) I use sendmail, but I'm thinking about switching to qmail in a near future..

BTW, which ont you think is best?.. sendmail or qmail... I haven't had any problem w sendmail... even after almos 2 years of uninterrumped operation.

by: egarciatPosted on 2005-03-07 at 16:56:51ID: 13482636

Wesly..

For som important internal reason, I need to send trough the outside SMTP server, ONLY THOSE rejected messages...

If I set a smart host, then all mail traffic will go to the outside SMTP wich is not good.. You may be thinking: it's the same trafiic... I know it, but we get charged in a "message basis" in the other server and there are no plans to changing to another due to contract restrictions.

by: wesly_chenPosted on 2005-03-07 at 17:01:02ID: 13482663

For Sendmail, add the following line into /etc/mail/sendmail.mc
define(`SMART_HOST',`<IP address of outside SMTP>') # <== replace <IP address ...> with the true IP, no <>

Then
make -C /etc/mail
and restart the sendmail.

For more details, check
http://www.sendmail.org/m4/masquerading.html

Sendmail and Qmail are both good. If you have use sendmail for 2 years without problem, then continue to use sendmail will be
easier for you.

Wesly

by: wesly_chenPosted on 2005-03-07 at 17:41:17ID: 13482825

> ONLY THOSE rejected messages...
Well, you got me. It is quite complicated.
You need to be able to process those rejected mail and substract out the "To:" field and forward to those emails the other SMTP server.

I don't have any specific way come to my brain so far.

Wesly

by: jleviePosted on 2005-03-07 at 19:11:00ID: 13483155

One problem with trying to use an alternate SMTP relay only if the message can't be delivered as a result of you network being blacklisted is that not all Internet servers will actually reject the message. Some mail servers will simply silently discard the message if it violates any of their anti-spam measures, including being on a blacklist.

Even if you could live with that you'd really need a custom version of Sendmail (or Qmail, or any other MTA for that matter). The user should get a bounce on a reject, but dealing with it there gets real unwieldly. you'd really want to catch the reject at the SMTP transport level and then move the message to a different queue used to relay through some other SMTP server.

Given how much work it is going to be to implement what you really want to do, I think a more profitable approach would be just to use SMART HOST and relay all outbound mail via that SMTP server. If it is reasonably well connected there should be little additional delay in delivery.

by: wesly_chenPosted on 2005-03-07 at 19:52:08ID: 13483317

Hi jlevie,

I think egarciat's concern is Money, which the relay server charges by per mail.

Anyway, I agree with jlevie since the way you want will take a lot of effort to implement and you might still lose the important emails if the
receiver doesn't reject the email....

Regards,

Wesly

by: jleviePosted on 2005-03-07 at 19:59:12ID: 13483349

Wesley,
> I think egarciat's concern is Money, which the relay server charges by per mail.

Could well be... But I really think that what he's asking for is a lot of work to implement and won't work in a significant number of cases.

by: egarciatPosted on 2005-03-08 at 11:31:05ID: 13489455

mhmh I think this problem doesn't have solution, at least a cheap, elegant solution, becuase I could write a script that tries to find some words like "rejected" on the "postmaster" account and then parse it's contents in order to get the To: field. But thats not elegant and can lead to failures.

Just like Wesley pointed out, there is no guarantee that the destination server, return a bounce message... I didn't knew that...

jlevie: Yes Money is concern, we got charged for every message sent, I know that's stupid, but we have a contract with that provider and can not stop using it, at least for the next 2 years. :)

by: wesly_chenPosted on 2005-03-08 at 12:41:49ID: 13490100

> can not stop using it, at least for the next 2 years.
How much for the penalty of breaking contract?
If charge by message base, then how much you need to pay monthly without using it (I mean still keep contact but not sending any
message to it)?
I would recommend that either to deal with your ISP for blacklist issue or switch to different ISP to eliminate the fundamental issue.

The emails being rejected/bounce could be
1. email account not exist,
2. receiptants out of quota,
3. internet routing break down during the delivery,
4. Blacklist,
5. typo on the receiptant,
6. spam source from the your mail server, such marketing announcement or advertising or one of your PCs get virus and become spam source.

You need to distingish the difference between those returned emails so you only send those blacklist one to the outside relay server.
Otherwise, you may also forward a lot of junks mail to the relay server, which costs money.
Besides, those emails sent to drop-by-blacklist mail server may be also very important and you assume the receiptants receive it since
you doesn't get the rejected. (As administrator, I will drop those emails instead of rejecting for security.)
What will be the business lost due to those kind of mistakes?

For business, I highly recommend to choose a reliable ISP for your internet connection without this kind of blacklist hassle.
Otherwise, you might be very busy to tune the script and fall into those potential bussiness lost without notice.

Regards,

Wesly

by: egarciatPosted on 2005-03-26 at 20:28:23ID: 13638239

I would like to close this question, and get the points back to me.. not because users don't deserve it, it's just that by the question's nature there is no solution for it.. I use to PAQ all my correctly answered questions.. but I think this one is not giving me a solution..

am I worng? :)

How can I close it and get my points back?..

Thanks

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if mail is rejected send it using antoher SMTP server.

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