Unable to send e-mail. Contact the site administrator if the problem persists.

Does any one know how to hide this error from the user. If the email module is unable to send email then log a message but don’t display it since it is not important.

Sometimes when the user submits Form to upload file, this error shows up. The only email that gets sent is email to our admin, so if we miss that email is ok. I am looking for a way to not display error about email error since the form submit is always successful.

Any idea which module generate this error to the user screen after form submit?

Drupal version: 

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