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Exchange minimum retry time

I got a call from a customer telling me that our emails to his provider where blocked because we are not complying with the SMTP protocol.
Our server was added to a grey list for anti spamming.

I was told that our email server (EXCHANGE-CGN) is sending retries too quickly.

What did happen?

The provider did check their trace logs:

The remote mail server was busy and did send a busy message to our server.
Our server did then resend the email after 4 minutes.
This is, based on information of the provider, too fast.
I am told by them that The SMTP protocol says that the minimum retry time is 5 minutes.

My question is where can I check to see what the minimum retry time is in exchange.

Thanks,
Rory

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rorybrady
Asked:
rorybrady
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1 Solution
 
rakeshmiglaniCommented:
i think there is a setting on the default smtp virtual server which defines the retry interval. have you checked it?
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rorybradyAuthor Commented:
Ya I think so all of the settings are set to 10 Min +
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ari24Commented:
If you recently changed the retry interval, you will need to restart the smtp service for it to take effect.
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rorybradyAuthor Commented:
No changes have been made it looks like this was orginally setup using the default settings.
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ari24Commented:
Do you have multiple outgoing servers? Make sure your retries are coming from the same IP!!!


Also a quick explanation of greylisting:
You werent added to a "grey list"... greylisting is a form of antispam that relies on the fact that most sources of spam dont behave in the same manner as regular mail servers. They basically employ a "fire & forget" type of scheme and will not retry sending a spam if it rejected once. RFC compliant servers will attempt retries after a specified period of time. As long as that time period is longer than the setting on the server doing the greylisting, and the IP of the host attempting delivery, the envelope sender address, and the envelope recipient address are all the same on the retry, the server will accept the message.
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jar3817Commented:
This doesn't make much sense. Sure you get greylisted the first attempt, and will every other attempt until a certain time limit has passed, which is set by the people who run the server performing the greylisting. Once that specified time is up the next attempt to deliver the message should be accepted. It shouldn't matter that you retry too fast, you could retry every 5 seconds if you want (but I don't recommend) and the message still won't be accepted until the right amount of time has past. But the next time after that limit is up I'll be accepted. So your first retry is too soon, so what? The next one (probably another 4 minutes later) should be accepted.  

If the receiving server is blacklisting you because you retry too soon that is their problem for having their server set too strict. Complaining about a minute here or there is a little rediculous.
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rorybradyAuthor Commented:
These are our Delivery Option settings:

First retry interval: 10 min
Second Retry interval 10 min
Third Retry interval 10 min
Subsequent retry interval 15 min
Delay notification 12 hours
Expiration Timeout: 2 days

In my understanding this is how our server should react to a busy message from anouther server. Could this be a problem with the configuration of there server? Or am I not looking in the right place?

thanks for all of your guys/girls help.

cheers,
rory
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ari24Commented:
Again, do you have multiple outgoing servers? Make sure your retries are coming from the same IP.
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rorybradyAuthor Commented:
We have a few outgoing servers as we have many remote offices.

How do I check: "Make sure your retries are coming from the same IP."

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ari24Commented:
Also, it sounds like you might be using a smtp connector, which would make your delivery retry options useless.
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rorybradyAuthor Commented:
How would I check these things?
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SembeeCommented:
An SMTP Connector doesn't have any retry times on it, so there is nothing to set on there.
Is there anything else installed on this machine? Antivirus, antispam? Something that could be interfering with the traffic?

It appears to me that most deployments of greylisting are flawed. It seems to be the new weapon of choice for spam, but isn't being deployed properly. I have seen greylisting deployed where the SMTP error code sent back wasn't deferred, but failure, meaning that the message was NDR'd.

Simon.
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rorybradyAuthor Commented:
There seems to be some conflicting opinions here. air24, it looks like we do have an smtp connector and you say that this makes our delivery options usless. Sembee says that there is no retry times on a connector which is true. So how would an smtp connector render the delivery options useless?

Thanks,
Rory
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SembeeCommented:
The only reason I can think that the retry times are nullified by the SMTP Connector is if a smart host is being used. In that case the retry times on the smart host server would be what is used.

Simon.
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rorybradyAuthor Commented:
You will have to excuse my ignorance on this subject this stuff is pretty new to me. Do you know how I would check the retry times on the smart host?

Thanks,
Rory
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SembeeCommented:
You can't.
The smart host would be something like your ISPs email server.
Do you have a smart host in the SMTP Connector?

Simon.
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rorybradyAuthor Commented:
I think the smart host setup for this connector is our head offices exchange server.


Remote Bridgehead

Server: Head office Exchange server
Virtual Server: Routing

Genral Tab
Connects this routing group with:
Head Office
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SembeeCommented:
Routing Group connectors and SMTP Connectors are two different things.
However if you have an SMTP Connector with the head office Exchange server as the bridgehead, then it is that SMTP virtual server on that machine that needs to be checked.

Simon.
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rorybradyAuthor Commented:
We have our proxy server set up as the smart host. Do you know where I would find the retry times on the smart host?
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SembeeCommented:
Depends what you are using on the server. If it is IIS, then you will need to look at the SMTP server settings.

Simon.
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rorybradyAuthor Commented:
Where in IIS do I change these settings?

I appreciate you patience!
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rorybradyAuthor Commented:
This looks like a problem on the clients side. The settings in IIS for Retrys is as follows:

First retry interval: 15 min
Second Retry interval 30 min
Third Retry interval 60 min
Subsequent retry interval 240 min
Delay notification 12 hours
Expiration Timeout: 2 days

What do you think?
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SembeeCommented:
Those look like standard settings. Certainly not as short as the time reporting in the original message.

Simon.
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rorybradyAuthor Commented:
Thanks fo rall of your help Sembee, you were dinamite!!
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