How to fix “SMTP Error: Could not connect to SMTP host.” in Linux reseller hosting?

Emails play a crucial role in online businesses. It can be bothersome when emails stop working.One such commonly encountered error is “SMTP Error: Could not connect to SMTP host.” Email messages are relayed through email servers, which are provided by all Internet service providers (ISP).These emails can be sent for various purposes such as order confirmations, invoice delivery, contact form submissions, password resets, account registration and so on.

But due to any issues related to email server or configuration, this mail delivery can fail and give out the error “SMTP Error: Could not connect to SMTP host.”A number of reasons can lead to the SMTP connection error.

1.Security restrictions

2.Mail server configuration

3.Client side mail settings

4.Software errors

Exim servers have some security restrictions to avoid outbound spamming mail issues and to protect server IP reputation from blacklists. These restrictions can lead to SMTP errors.Another setting in WHM that provides the same restriction is, “WHM Home » Security Center » SMTP Restrictions”. This prevents users from bypassing the mail server to send mail.Firewall rules can be configured to selectively or fully block connectivity to the SMTP ports.

The SMTP server is often specified as a hostname in the mail settings of the software. A DNS failure or temporary issues can affect the name resolution of the mail server.If the OpenSSL module is not configured properly or if the PHP extension is not working fine, it will throw errors during SMTP connections.

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

Once the cause for the error is identified, we make appropriate fixes such as re-configuring firewall rules and tweaking the security settings, so that mail delivery works fine.