cURL errors often relate to your server, not the SMTP plugin you use. It usually indicates that your server’s cURL library is outdated.
You may also experience this error if your SMTP server (mailer) is incompatible with your server’s cURL version.
Oftentimes, the cURL error might have a number next to it. An example is the cURL error 28. Regardless of the number you may see, it generally means the same thing – your server’s cURL version is outdated.
Resolving the Error – Solution
To quickly resolve this error, you’ll need to update your server’s cURL library. The steps to update this library will differ depending on your web hosting provider.
We recommend getting in touch with your web hosting support for guidance. They should be able to update the library on your server.
Another solution to this error is switching to a different mailer if the one you configured is incompatible with your server. We recommend using the SendLayer mailer instead, as it is proven to work without cURL-related issues.
Note: Want to learn how to configure the SendLayer mailer? Be sure to check out Easy WP SMTP’s tutorial for more details.