{Complete Solution} Solve SMTP Error: Could not Connect to SMTP Host

April 18, 2020

When it comes to an online business, Emails definitely play a crucial role. And thus email marketing has become one of the main modes of businesses online. It becomes bothersome when emails stop working as it may make you lose an urgent invite or important notification. Therefore to configure email services and assisting it to solve the email errors becomes important.  One such commonly encountered error is “SMTP Error: Could not connect to SMTP host.”

So in this guide, we will tell you the reasons behind this error and how to solve SMTP error: could not connect to SMTP host.

When do you see the Error- Unable to Connect to SMTP Host

You must be knowing that the majority of the SMB websites run on CMS such as WordPress, Joomla, WHMCS, etc. And most of this CMS software is configured to send emails from them only.

The process of email sending can be utilized for various purposes – such as password resets, account registration, order confirmations, invoice delivery, contact form submissions, and much more.

But due to any failure or issues related to email server or configuration, the purpose of mail delivery fails giving out the error “SMTP Error: Could not connect to SMTP host.”

The same error can also appear in different forms as-

SMTP -> ERROR: Failed to connect to server: (0)

SMTP Error: Could not connect to SMTP host. The message could not be sent.

Mailer Error: SMTP Error: Could not connect to SMTP host.

‘SMTP connect () failed’

Causes of the Email Error “Unable to Connect to SMTP Host”

There is a number of reasons which can lead to the SMTP connection error.

  1. Mail server configuration

Talking about the first reason it can be due to mail server configuration as the SMTP server is often specified as a hostname in the mail settings of the software. Therefore a DNS failure or temporary issues can affect the name resolution of this mail server.

In such cases, the mailing software becomes unable to contact the SMTP server, thereby causing connection errors. If the mail server has another service running on the SMTP port configured, the same issue may occur.

Another issue that is related to the mail server is the lack of support for encryption. If the OpenSSL module is misconfigured or if the PHP extension is not working well, it will toss errors during SMTP connections.

  1. Security restrictions

Exim servers, by default, pose some security restrictions to avoid outbound spamming and protect server IP reputation from blacklists. These restrictions but lead to SMTP errors.

The setting in WHM ‘Server Configuration > Tweak Settings > Mail => ‘Restrict outgoing SMTP to root, Exim, and mailman’, blocks outgoing SMTP from website software.

Another setting in WHM that comes with the same restriction is, “WHM Home » Security Center » SMTP Restrictions”. This prevents users from bypassing the mail server to send mail.

Further, website owners who use Gmail as their SMTP server face further security restrictions imposed by Google. By default, Gmail will not allow connections from third party software.

If the option “access for less secure apps” is not enabled in the Gmail account, users get the error “Unable to connect to SMTP host” on their websites.

  1. Client-side mail settings

To send mails from website software, you will require to configure the settings such as SMTP host, port and mail account username and password.

But even a single configuration mistake in these settings may lead to email errors due to authentication failures showing the message “Unable to connect to SMTP host”.

If the connection is attempted to a different mail server, it might not work. This can happen especially in the cases of website migration from one server to another.

Also, when encryption is not chosen for mail settings, many mail servers can reject the connection attempt.

  1. Software errors

Many website owners customize their software with plugins to enable them to send mails. Many others have custom code and tweaks done in their CMS.

Due to software updates, feature modifications, plugin issue or other code related bugs, the SMTP authentication support can stop working, giving out SMTP errors in the site.

How we Solve SMTP Error: could not connect to SMTP host error?

To fix the error, first, examine the software settings, test the connectivity to mail server, and other security restrictions in the server to find the issue.

Once you have identified the cause for the error then follow the appropriate fixes such as re-configuring firewall rules and tweaking the security settings, to make sure that the mail delivery works fine.

For software updates and installs, you need to take proper backups and even may require to conduct mock installs beforehand, which will help you to perform upgrades and fixes in websites without causing any errors.

Wrapping Up!

Email errors are no doubt the most commonly encountered issues in servers. And so here was the guide on how to fix the error “Unable to connect to SMTP host” in websites.



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{"email":"Email address invalid","url":"Website address invalid","required":"Required field missing"}