By far the most popular auto responder service is AWeber Communications. At about $20 per month, Aweber provides capabilities far beyond its competition at an affordable rate! Here are a few of the features:
An integral part of having reliable email deliverability is ensuring that only specifically requested information is sent to subscribers. Watching and working with customers to prevent them from inadvertently or purposely sending unsolicited email is a large part of consistent deliverability. Avoid services that offer free accounts or free trials as these are havens for abuse and people take advantage of them to send spam negatively impacting email deliverability.