Exchange Server

iis_iis · Guest

Hi,

I have a 2003 server and it exhibits some strange behavior so I do not know
how to fix it. I have tried everything, as suggested by Microsoft - for the
specific error(s), with no avail.

The server is a Dell computer with Windows 2003 Server (Domain Controller)
and Exchange 2003 running on the same box. Actually this is the only box on
the domain. Exchange 2003 is at SP2, the OS has all security patches
available installed. There is no antivirus (OS or email) on it at this time.

The network configuration is as follows: ADSL, Netopia DSL router. The email
server is NAT-ed using a 192.168.1.X IP and the public IP (on the DSL router)
xxx.xxx.xxx.xxx resolves to xxxx.dyndns.org. The router allows SMTP, HTTPS,
IMAP to pass through for the email server’s IP.

I send/receive emails with IMAP and OWA and all works fine, no problems –
but only when I am NOT connected to the same network! When I connect either
wireless or directly to one of the router’s LAN ports, I cannot send emails.
The interesting part is that I cannot send with either IMAP or OWA – both of
them will timeout. The message when using IMAP is, after about 30 sec:
- Your server has unexpectedly terminated the connection. Possible causes
for this include server problems, network problems, or a long period of
inactivity. Subject 'Re: TSq', Account: 'xxxx.dyndns.org', Server:
'xxxx.dyndns.org', Protocol: SMTP, Port: 25, Secure(SSL): No, Socket Error:
10053, Error Number: 0x800CCC0F

The message when using OWA is: after about 1min a window will pop-up with a
yellow exclamation sign and the word UNKNOWN in the middle.

Here comes the interesting part. If I connect with the VPN to my work
network and try to resend the message – it works! It also works if I am
anywhere else connected to the Internet but not on the network where the
email server is.

There is a more interesting behavior. If I try to send a test message with
only a few words, the message goes through, NO error. If I write 4-5 words
and try to send an email it will NOT work. The same - will not work - if I
try to reply to an email, probably because it increases slightly in size –
but works fine if I connect with the VPN to my work place and try to send or
reply to the same email. It appears that only small emails can go through but
not larger ones.

I have enabled the logging and there is not much I can see, only noticed
that after HELO and other instructions there is no DATA entry when the email
fails (In the IIS SMTP log). The same email will have a DATA entry in the log
when trying to send the same email but after connected with the VPN – so,
from the outside network.

I have noticed that in the Application log (OS), there are entries that say
something like user xxxxxx connected from xxx.xxx.xxx.xxx and then it doesn’t
work, but when I connect through the VPN and it works, it says user xxxxxxx
connected from xxx.xxx.xxx.xxx - the IP at work (from the VPN). The computers
I try to send emails from are all connected to the same DSL router – either
LAN or wireless. Anyone knows if there is something in the Exchange or
Windows 2003 that will prevent a user (domain admin or just regular user – I
have tried with different accounts) to logon and send email when coming –
apparently – from the same IP as the server’s default domain (although the
server is NAT-ed, the public IP actually resolves to xxxx.dyndns.org which is
the domain for the email server). Why is it working if I am not on the same
network with the email server but not when I am connected to the same router
as the server?

I have tried all methods suggested in kbs -I could find- for these specific
errors: no av software, no firewall, IIS bandwidth throttling, different XP
computers with SP1 or SP2, even a PDA, with the same negative result. The
only one I cannot try is the MTU as the Netopia DSL router doesn’t have a way
to tweak the MTU. I saw that some Linksys DSL routers have this issue.

Sorry for the long post but I believe this is a pretty interesting issue. I
have seen that other people had similar problems but I could not find a fix
for this particular one. This is not related but it may be a similar
“security feature”, someone may be aware of. I know that for security reasons
(last year), one Windows hotfix disabled the ability to connect with the VPN
if you come from the same subnet/network as the VPN server. This email
behavior is similar but still not consistent so it may not be the same as the
emails go through if small, a few words, but timeout and fail if they have
4-5 words or bigger.

Thank you,

IIS

iis_iis · Guest

Nevermind, I figured it out...

Thanks,

IIS

"iis_iis" wrote:

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