?
Solved

SMTP Connection Timeout on Guest Linux OS to Remote Exchange Server

Posted on 2009-07-14
5
Medium Priority
?
820 Views
Last Modified: 2013-11-11
Hi,

we are running ESXi 4 and have some VMs installed. One is a Linux (CentOS 5.3) and one is a Windows 2003 server.

The Linux machine cannot send email to a remote Exchange server. The Windows server has no problems.

When using telnet on the Linux machine to port 25 on the remote server, it connects, but hangs on the line: escape character is ].

After some Enters, the welcome message from Exchange mailserver is shown and the HELO command etc. can be entered.

The windows server connects immediately to the mailserver and displays the message.

Also when sending a mail to a recipient on the exchange server through EXIM commandline, this generates a timeout. (another linux server in the same rack, not a VM, can send mail and telnet correctly to the remote server.). I also tested another exhcange mailserver and this one also generates a timeout. One more exchange server is connection as it should.

I tried disabling SELinux and IPtables. Even tried bypassing the hardware firewall. Also I have installed another Linux distribution. None of these have the desired effect.

ReverseDNS is working OK. Hostnames can be resolved. This all works.

Does anybody have an idea what to do next?
0
Comment
Question by:gaffie
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
  • 3
  • 2
5 Comments
 
LVL 65

Expert Comment

by:Mestha
ID: 24851697
That sounds like classic interference.
What else is on the Exchange server? AV, Antispam?

Have you checked the network card drivers are up to date?

Simon.
0
 
LVL 4

Author Comment

by:gaffie
ID: 24853181
Well, the mail servers (Exchange) are all three receiving mail perfectly. Just not from our Linux servers on ESXi. Also, the Linux server (non VM) behind the same firewall as the VM Linux is able to connect without any problems. The Windows server (VM) is also able to connect without problems.

I have added an image of the situation, maybe this will make it easier to understand the problem.

There are five locations in the image.
Location A: Our rackspace in the datacentre with two physical servers. One ESXi and one Linux. On the ESXi there are two VM's. One Linux and one Windows. These are behind the same firewall (cisco ASA).
Location B is another rackspace Linux server at another datacentre.
Location C is our own Exchange server at the office.
Location D and E are a clients with Exchange servers.

From location A telnet (or sending mail with Exim) fails from LinuxVM to Location D and E.
From location A telnet (or sending mail with Exim) is successful  from:
- LinuxVM to location B and C.
- WindowsVM to location B, C, D and E.

From location B telnet (or sending mail with Sendmail) is successful  from:
- Linux to location A, C, D and E

I hope this better explains the weird problem.







EsxiSMtpSituation.jpg
0
 
LVL 65

Expert Comment

by:Mestha
ID: 24854829
Have you got the SMTP scanning feature turned off in the ASA? I have seen that provide odd results more than once and turn it off by default.

Simon.
0
 
LVL 4

Author Comment

by:gaffie
ID: 24857384
We have tried the smtp scanning feature, both on and off, without any success.
0
 
LVL 4

Accepted Solution

by:
gaffie earned 0 total points
ID: 24870789
Solved! The problem was the firewall. Both clients had a Zyxel Zywall 5 and apparently the firmware 4.00 has a bug that causes this error. Upgrading to the latest (4.04) firmware solved the problem. The other client also had a Zywall, but had already firmware 4.04 installed.
0

Featured Post

Video: Liquid Web Managed WordPress Comparisons

If you run run a WordPress, you understand the potential headaches you may face when updating your plugins and themes. Do you choose to update on the fly and risk taking down your site; or do you set up a staging, keep it in sync with your live site and use that to test updates?

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Local Continuous Replication is a cost effective and quick way of backing up Exchange server data. The following article describes the steps required to configure Local Continuous Replication. Also, the article tells you how to restore from a backup…
Marketers need statistics and metrics like everybody else needs oxygen. In this article we explain how to enable marketing campaign statistics for Microsoft Exchange mail.
In this video we show how to create a mailbox database in Exchange 2013. We show this process by using the Exchange Admin Center. Log into Exchange Admin Center.: First we need to log into the Exchange Admin Center. Navigate to the Servers >> Data…
To show how to create a transport rule in Exchange 2013. We show this process by using the Exchange Admin Center. Log into Exchange Admin Center.: First we need to log into the Exchange Admin Center. Navigate to the Mail Flow >> Rules tab.:  To cr…
Suggested Courses
Course of the Month10 days, 23 hours left to enroll

770 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question