[Plugin: BigContact] Cannot Send Email: Internal Error

I was using WP 3.5

first of all thanks for the great plugin.
error is showing but i can receive the email. some people continuing send the emails because the error.
WP 3.5 and bigcontact 1.4

ba tashakor

Had the Internal error.
The issue on my Windows v-box was, that checkdnsrr is undefined in my PHP version.
I modified the plugins code to check for the availability of the function before calling it to double check the mail address.