There is better way to avoid this in Google Apps for Business.

To avoid such scenario you have to add SPF record in your DNS manager at your hosting side.
This SPF record authenticates your mail and avoid it from getting marked as spam.
This also avoids bounce back messages which are rejected by the server under the category of spam.
You have to create a TXT Record in your DNS manager of your domain.

SPF record  v=spf1 ~all

Also refer following link