Aweber & Getresponse are still the industry leaders when it comes to reliable, fully functioning Autoresponders. We understand that you might already use another Autoresponder, and we do have plans to integrate additional ARs in the future but for now it is just Aweber & Getresponse.
If you are already paying for another AR and consider using another may be an additional cost you could do without, please remember you can get a free Aweber account through the button in your BLOX dash, a free account does have some limitations as mentioned in full on this page. But those limitations will still enable you to run one BLOX system up to 500 leads, and at that point you should have made many, many times the cost of upgrading your Aweber account in commission.