Error: SMTP error: could not connect to SMTP host

What's Causing This Error

This issue for this error is the inability to establish a connection with the email server. Connection issues may vary depending on the scenario. However, there are some common aspects that you may need to validate before proceeding further.

1. Security Restrictions.
2. Temporary connection issues.
3. Invalid client-side settings.
4. Email hosting provider limitations.

Solution - Here's How To Resolve It

It is essential to go through the following items while ensuring that each configuration is valid.

1. Security Restrictions - Some email servers, such as the Exim server, comes pre-built with security restrictions to prevent outbound spamming. These restrictions, however, can also bring about errors when the user is attempting to send a large number of emails for a legitimate reason. Therefore make sure that all default security restrictions do not get in the way of operations.
2. Temporary connection issues - Ensure that the client has unrestricted access to the email server to establish a connection. One of the most common troubleshooting steps is to check if the email server domain is resolvable from the client. The troubleshooting can move to check for network connectivity issues.
3. Invalid client-side settings - The email client requires settings for connecting to the email server. These settings can include hostnames, ports, encryption settings, etc. It is essential to make sure that all the configurations made to the client are according to the email server's compatible settings.
4. Email hosting provider limitations - Some web hosting providers may impose limitations when using third-party email hosting providers. This tactic forces users to use the hosting provider's email service rather than a third-party service. It is essential to clarify the limitations and the compatibility recommendations before selecting a hosting provider.