451: read error

[cmaxwell]

Hi all,

Kind of pulling my hair out with this one.

We have a customer who has recently transferred their domain to us. The server's running Plesk 7.5.4 and requires SMTP auth for sending mail.

The customer is on AOL broadband and are using MS Outlook 2003. They can receive mail but cannot send mail and get this error in a bounce message after sending mail:

The original message was received at Mon, 16 Jan 2006 06:54:47 -0500 from smtp-los03.proxy.aol.com [195.93.24.41]

----- The following addresses had permanent fatal errors ----- <support@DOMAIN>

----- Transcript of session follows -----
451 4.4.1 reply: read error from mail.DOMAIN.
<support@DOMAIN>... Deferred: Connection timed out with mxbackup.DOMAIN.
Message could not be delivered for 2 hours Message will be deleted from queue

I've replaced the actual domain in the example above with DOMAIN for privacy.

The line "Deferred: Connection timed out" is fine as we have established the secondary MX is extinct, but the primary mail server is fine and I can send/receive messages from the same account without errors but the customer still can't.

Not sure if AOL don't allow their customers to use external SMTP servers or if they replace requests to use external servers with their own servers. The customer says he has "mail.DOMAIN" set as his outgoing mail server with outgoing authentication enabled, yet the error message indicates an AOL server...

Does anyone have any ideas? Short of going to the customer's office I am at a loss as to what to do and they are getting more and more aggravated as it was working before they transferred...

Thanks.

- Chris

 

[cmaxwell]

Finally managed to work this one out - after lots of searching I found out that AOL use an SMTP proxy for any outgoing connections on port 25. So if he's got mail.domain.com set as his outgoing server in Outlook, AOL still intervene and replace it with their unreliable SMTP proxy.

I set up IPtables to forward connections on port 2525 to port 25, and the client now has his SMTP server set to mail.domain.com on port 2525 and it works like a charm.

A long way for a shortcut - but not impressed with AOL's thwarted approach to SMTP.

- Chris