I tried with Interspire from our own server. The problem was that we got banned (our domain name) from some local ISPs... This was killing our business, so that´s why I'm looking for alternatives that are "not connected" to our domain name. I'm not sure if AWeber would be better as many of you suggest. We only send to our own customer list (potential customer list), but any way we got banned already after 1000 emails... Are there any general guidelines you need to follow not to risk getting banned?
Your best bet is to use an autoresponder like Aweber or Getresponse, ofcourse people have to subscribe to your autoresponder before getting your mail
When you send bulk emails, first make sure your messages do not violate the Acceptable Use Policy (AUP) of email or internet service providers.
Aweber gets my vote too - I've been using it for over four years now, and it's made me thousands of dollars over the years. Can't imagine online marketing without it.