Resolving Outlook error 0x80042109 in DirectAdmin web hosting servers – How ISP port 25 block, server and PC firewall issues cause SMTP connection errors

Task ‘account@domain.com – Sending’ reported error (0x80042109) : ‘Outlook cannot connect to your outgoing (SMTP) e-mail server. If you continue to receive this message, contact your server administrator or Internet service provider (ISP).’

If you are a DirectAdmin web host, this would be a common error reported by your customers who use Outlook.

A one-size-fit-all solution is not possible for this error as the issue might be in the PC/Laptop, at the ISP or even at your server.

Help desk support services at Bobcares engage each web master on a step-by-step trouble shooting process, which determines exactly where the issue is, and solves the specific issue that caused the error. Here’s a quick run down on the various issues that can cause Outlook error 0x80042109.

 

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PC/Laptop configuration issues

Though pretty rare, third party firewalls and anti-virus software are known to block connection to certain IP ranges, which could include your server IP as well. In our troubleshooting, if we do not see a recent connection from the customer to our server, this is a possibility we investigate.

Some web masters would have duplicate profiles which will have an old mail server configured in it, and therefore would be trying to connect to the wrong mail server. When we do not see recent POP/IMAP requests, this possibility is also investigated.

ISP firewall issues

Some ISPs are known to block traffic through port 25 to minimize automated spam. This is the most common reason for Outlook error 0x80042109. We enable an alternate SMTP port in our DirectAdmin servers to by-pass this block. This is enabled by adding the following line on top of /etc/exim.conf, and restarting Exim.

daemon_smtp_ports = 25 : 587

# /sbin/service exim restart

We usually give the port number 587 as it is a standard SMTP port, and would therefore likely to be white-listed in third party PC firewalls and anti-virus. Along with enabling the port in Exim, we also add this port to the firewall white-list to allow incoming connections.

Another very rare variation of ISP level problem is when the Internet Exchange Point (IXP) of a country might not be relaying traffic to your server IP block. When a significantly large number of customers from the same geo location reports connectivity issues, this is an option we think about.

Server firewall issues

Occasionally server firewalls can block certain IPs or IP ranges based on anomalous behavior. Looking for the customer’s IP in the server’s firewall is one of the first things we do when we don’t see a recent connection on other service logs. In servers using iptables, the following commands are used to de-list an IP.

# iptables -L INPUT -v -n | grep "xxx.xxx.xxx.xxx"
# iptables -D INPUT -s xxx.xxx.xxx.xxx -j DROP
# service iptables save

NOTE : If you use a firewall manager like CSF, make sure you de-list using that instead of direct de-listing from iptables.

The above were some common reasons for Outlook error 0x80042109. In web hosting support, each support request is unique. A long chain of possibilities exist that may have resulted in the issue. In our Help desk support services, we treat each customer as unique, and explore all possibilities before giving a final solution.

Looking for a better help desk support experience for your customers? Check out our Help Desk support features below:

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Bobcares
Bobcares is a server management company that helps businesses deliver uninterrupted and secure online services. Our engineers manage close to 51,500 servers that include virtualized servers, cloud infrastructure, physical server clusters, and more.
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