Re: SBS2008 / Exchange with POP3 Connector / Invalid Header Fields - problem

Thanks about very fast answer Lanwench.

This is not my own server, it is my customers server, and main problem is that they absolutely want to keep that wäy.
So POP3 Connector has to stay there, and we have to use it.

Well, I really need answer to that question, please.
Jani

Pitti <pitti@xxxxxxxxxxxxxxx> wrote:
Hello,

Hello ...my reply is at the bottom.
I have had this problem long time now, and I have been received a very
good trick from "Dan Thompson [MSFT]" / March 2009.
That trick helped me a lot, but didn't give me total fix to the
problem.
Problem is that SBS2008 POP3 Connector is trying to deliver emails to
Exchange Server, but fails because those emails are not "standard"
emails. Every email, that is "standard" email, are delivered just fine
to Exchange, but those emails, that aren't "standards" are still
staying on ISP's POP3 Email Server.
Non "standard" email has return path: mailer-daemon - text, and that
makes it non-standard email.
Exchange server has some kind of "filter", which says that this email
cannot be received at all, so it will be rejected. If someone knows
how this "filter" will be disabled, I would be very pleased about
quidance.
Here is quote about Dan Thompson technical description:
Also found in this web site
http://www.tech-archive.net/Archive/Windows/microsoft.public.windows.server.sbs/2009-03/msg00163.html

Exchange will close an SMTP connection after a certain number of
protocol errors (5 by default). (see the MaxProtocolErrors property of
the ReceiveConnector object at:
http://technet.microsoft.com/en-us/library/aa998618.aspx)

When the SBS 2008 pop3connector downloads a message from a POP3
mailbox, it needs to figure out what the "return path" for the mail
should be, which it does by reading the email's headers. The
pop3connector does not do validation of the header value--it lets
Exchange take care of that. If the header value that the pop3connector chooses is malformed, when
it is sent to the Exchange server (as part of the "MAIL FROM"
command), Exchange will reject it with a 501 error. That counts as a
"protocol error", and therefore is counted against the
MaxProtocolErrors limit. Since the pop3connector was not able to
deliver the mail, and does not know if the mail is safe to delete, it
leaves the mail on the POP3 server.
If there are 5 of these messages in your POP3 mailbox, then there will
be 5 "protocol errors" in the pop3connector's SMTP session, which hits
the limit, and Exchange will end the session with a transient error
(4xx). When this happens, the pop3connector recognizes that the error
is transient, and will retry again at the next scheduled download
period. But since those 5 malformed messages are still in the POP3
mailbox, the same thing will continue to happen, with no "forward
progress" being made.
The workaround is to increase the “MaxProtocolErrors” property of the
internal receive connector, which is called “<COMPUTERNAME>\Windows
SBS Fax Sharepoint Receive <COMPUTERNAME>”, and then restart the
Exchange Transport service for the change to take effect (and you’ll
have to restart the pop3connector service, too, since it depends on
the Exchange Transport service). Unfortunately, you can’t set that
property from the Exchange management GUI, so you have to do it from
an (elevated) Exchange Powershell prompt. Here are the instructions:


From an elevated Exchange Management Shell (Exchange Powershell
window) (right click on “Start-->Microsoft Exchange Server
2007-->Exchange Management Shell” and then choose “Run as
administrator”) run the following Powershell commands:

Set-ReceiveConnector -Identity ($Env:computername + "\Windows SBS Fax
Sharepoint Receive " + $Env:computername) -MaxProtocolErrors 500
Stop-Service pop3connector
Restart-Service -force MSExchangeTransport
Start-Service pop3connector

That will increase the MaxProtocol errors (of the internal receive
connector only) to match the pop3connector’s max emails downloaded per
session. Once you get 500 messages with malformed headers stacked up
in the POP3 mailbox, though, you’ll still have to delete them
manually.
Q. Why might you be getting emails with malformed headers?
A. It seems there are some buggy (perhaps deliberately) spam servers
out there. Or it could be non-compliant mail software (like whatever
software generated "Return-Path: <MAILER-DAEMON>" header that started
this thread).

Thanks for advance!
Jani

Hi - short answer to a long post. Do not use the POP connector. Host your own mail directly. This problem and many many (many many many) others will go away.


.

Relevant Pages

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