How to resolve ‘Outlook cannot connect to SMTP server’ error
Often web hosts get contacted by account owners who are unable to send or receive emails via Outlook. The error message they see in their Outlook would be:
Task 'email@example.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)."
In our role as Website Support for web hosting companies, this is a concern we quickly resolve for users who have email accounts hosted in the customers’ servers.
As a one-size-fit-all solution is not possible for this error, today we’ll see what are the common causes for this error and how we resolve them for the customers.
What causes ‘Outlook cannot connect to SMTP server’ error
The SMTP error in Outlook can happen due to many reasons, broadly classified into these categories – 1. User end issues 2. ISP issues 3. Server side issues.
1. PC/Laptop firewall issues
Though not so common, third party firewalls and anti-virus software in user PCs can block connection to certain IP ranges, which could include the server IP as well. This can give errors while connecting to the mail server for sending or receiving mails.
To check the connectivity issues from user’s PC or laptop to the mail server, we get the results of ‘telnet domain.com 25’ from the users, which shows whether the user is able to connect to the SMTP port in the mail server.
2. Outlook configuration mistakes
Most common reason for ‘Outlook cannot connect to SMTP server’ error is the wrong configuration settings of Outlook. This happens especially in the case of newly configured email accounts.
A mis-spelled mail server name to a wrong port setting in Outlook can cause connectivity issues to the mail server and end up giving error while trying to send or receive mails.
By default, the port settings for mail related services are these, and a connection problem to these ports can lead to Outlook error:
SMTP - port 25 / 587 POP3 - port 110 IMAP - port 143 Secure SMTP (SSMTP) - port 465 IMAP4 over SSL (IMAPS) - port 993 Secure POP3 (SSL-POP) - port 995
There are also chances that some web masters may have duplicate profiles in Outlook, which will have an old mail server configured in it, and therefore would be trying to connect to the wrong mail server.
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3. 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 ( ‘Outlook cannot connect to SMTP server’ ).
A ‘traceroute’ result to the mail server from the user end helps to reveal if there are any connectivity issues in any of the intermediate network between user PC and mail server.
4. Server firewall issues
Firewalls are the security barriers which we setup in servers to protect them from malicious attacks or hacks. Occasionally, these server firewalls can block certain IPs or IP ranges based on any anomalous behavior.
For instance, exceeding the login failure attempts or too many connection attempts to the server can lead to an IP address being blocked in the server firewall. This can lead to error ‘Outlook cannot connect to SMTP server’.
The above were some common reasons for Outlook error 0x80042109. In our website support services, we treat each customer as unique, and explore all possibilities before giving a final solution.