I think there are free and paid services, good and bad ones.
Among the paid services I do recommend only Aweber and Get response, but be aware that you will have to pay a monthly fee.
The question then is? Would you be paying monthly fees as long as you want to keep your lists? or are you going to HAVE YOUR OWN AUTORESPONDER on your own website? Without Monthly fees
If you go for the second option, this what I can help you with:
1- Give you a FREE To USE Autoresponder PHP script
2. For a small fee (that you can see on IBOGigs HERE, I can help you configure the following:
Your Squeeze page (including Freebie to your susbcribers and download page)
Your OTO is apply (in case you have soemthing of your own to sell)
Upload of files to yoru own server.
Just think about how much money you can save monthly, (From $14 to $19 a month), what about yearly?
Contact me for details (check my profile)