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How to resolve ‘Outlook cannot connect to SMTP server’ error

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 ' - 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.

Are you facing email errors in your site?



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 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.

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  1. Hi,

    this is the best support site I have ever visited.

    Thanks mate, you resolved my issue.

    I am 100% happy and hope you continue to do this wonderful work.


    • Thank you for the kind words Mansoor 🙂

  2. yo tenía el mismo problema, lo que hice fue restaurar a los valores predeterminados del firewall de windows y se solucionó el problema.

    • Thank you Joel. 🙂

      English translation of Joel’s comment :
      I had the same problem, what I did was restore to the default values of the windows firewall and the problem was solved.

  3. IT WORKED!!!!!! 587 was the magic number

    Over two hours trying to get this setup…


  4. Need help to resolve
    Task ‘ – Sending’ reported error (0x800CCC67) : ‘ The server responded: 421 please try again later’

  5. Thnx, using 587 port

  6. “Log onto incoming mail server (POP3): The operation timed out waiting for a response from the receiving (POP) server. If you continue to receive this message, contact your server administrator or Internet service provider (ISP).”

    Outlook 2013 settings are
    In 993 ssl
    out 587 ssl

    • Hi Phillip,

      Looks like either your POP3 server is down, or your network is is broken or your IP is blocked in the server.

      You can talk to our experts by clicking here if you are still facing this error.

  7. “Log onto incoming mail server (POP3): Outlook cannot connect to your incoming (POP3) e-mail server. If you continue to receive this message, contact your server administrator or Internet service provider (ISP).”

    I have kept receiving this message, which does not allow me to log on to my mail.

    Any assistance, please.

    • You can talk to our server admins by clicking on the chat icon on right bottom of this page.

  8. Thanks a lot.

    Very useful and fix my issue

  9. Hello,I have problem with old version ( 2007 and 2010) of office but new version it’s working normal ( 2013 and 2016).I try to config many day but still not working,I don’t want to reinstall the new version, Please help me guy

    • You can talk to our server admins by clicking on the chat icon on right bottom of this page.

  10. Hello,

    I’m having trouble setting up my outlook 2016.I tried with a gmail adress and Outlook tells me We couldn’t log on to the incoming imap server.I enabled imap in gmail’s settings,I allowed unsafe apps to acces my email but nothing works.


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