Message could not be delivered for 3 hours

Posted on 2010-08-30
Last Modified: 2012-05-10
I have a user that i have included to the whitelist (bypassed antispam rule) and I also added a keyword so email from a will go through.
The email to through but the user from aol is getting an error message " 451 4.4.1 reply: read error from
<>... Deferred: Connection timed out with
Message could not be delivered for 3 hours
Message will be deleted from queue"
Any suggestions on what should I do to prevent that user from getting that returned email message?
Please help.
Question by:jsistoza
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LVL 14

Accepted Solution

steveoskh earned 500 total points
ID: 33563545
Is your firewall patched to the latest release and firmware?

Author Comment

ID: 33563561
Yes. it only happens to one user outside the company. the recipient (inside the company) gets the email but the sender aol (outside) is getting the error message.
LVL 77

Expert Comment

ID: 33698684
This usually happens if the processing of the incoming mail is longer than the timeout of the sending server.
Does this only happen when the message that is being sent is large i.e. has an attachment?

I.e. sending mail server establishes a connection to your mail server. Exchanges SMTP pleasantries. Identifies the sender, the recipient and submits the message. The sending server is waiting for a status (2xx good, 4xx temporary error try again later, 5xx permanent error don't try again)
Your server than starts the various checks and takes some time.  the sending server is not seeing any response and at some point the connection is seen as dead either between their mail server and their proxy, their proxy and yours firewall, or between your firewall and your server, so the closing of the connection is started. To avoid data loss, these types of terminations, are interpreted as temporary error 4xx and could be generated by the sending mail server itself seeing the connection it had to the remote server is no longer there.

Author Comment

ID: 33701764
it only happens to one user from aol and it does not matter if it has an attachment or not. Also, sometimes the email gets through but still sends the error message to the sender. And some other times when the sender recieves the error and notifies me of the error, the logs does not have a record of that incident/error, as if it didnt get processed in the exchange.
Does that mean when aol sends an email, it gets blocked by my firewall?
What are some recommended resolution do you suggest?
Do I need to do more investigation of the problem?
What are some tools that you recommend me to use?
I have already posted problem ticket to aol's postmaster but im not sure if they are very good at answering their problem.
LVL 77

Expert Comment

ID: 33702616
Check the logs on your side to see what your mail server is reporting and if you have an smtp proxy gateway, check that as well.  Does the user get multiple copies of this message? Do the logs reflect multiple connection attempts from the sending server?

Are you saying that if the user sends a single line message, they get this notification as well.

The other item the sending user can check is whether every message they send has this behavior or does it match a specific AOL sending server. i.e. if the message hits there is no issue, but if it lands on, there is this delay.

It is up-to-you. If after looking at your side, you do not have a log entry dealing with terminating connection to

When you looked through your exchange logs, depending on how verbose they are, when the AOL message is seen, do you see the complete transaction in the logs?
helo received
status returned
mail from: received
status returned
rcpt to: received
status returned
data received
status returned
rset received
status acknowledging recipt
quit received
terminating connection.

if your server terminates the connection after the message is received and before it gets the quit notice from the remote server, this might explain this issue. Many servers  will treat the status returned after the data command as an acknowledgment that the message was successfully delivered without regard whether they were able to issue to rset and quit to complete the cycle.
AOL proprietary system might require the entire process to be treated as success such that a termination of the connection prior to the sending of quit by the AOL server is seen as a fault and that the message might not have been delivered.

I think you can sign up for an AOL/AIM account and test it yourself.  Send a message to your account on the exchange and see if you get the same result.  
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Author Comment

ID: 33703007
I thought this will be a simple fix but its turning out to be a big headache. I will do more testing and also check my firewall.
The most interesting aspect of this is other aol users does not get the same delayed error message only that specific user.
Thank you for the reply. I will definitely look into the things that you suggested.
LVL 77

Expert Comment

ID: 33703232
Good luck.  You need to see whether there is a pattern to when this type of error occurs. Time of day, Specific day, i.e. tuesday, size of message, etc. The sending server?  It might be that the user's geographic location may point to a cause.  Is the user have an AOL client installed on their system or are they accessing through a web page? etc.

Author Comment

ID: 33703294
its through an aol client version 9.1. And the time the error occurs are random. But i will check if its coming from a specific server or ip.

Thanks again!!

Author Comment

ID: 33962687
I have a third party provider that blocks ip address from my router. I have updated the routers version and corrected the error.
Also there are some very useful tips on Aol postmaster site.

Author Closing Comment

ID: 33962702
updated the firmware and the third party provider for blocking known bad ip address.

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