I have used Campaign Monitor for a number of years both for handling local club subscriber lists and emails through to business based solutions. With a variety of solutions including pay by campaign and monthly subscriptions, I have found it simple and effective to use.The interface for designing and email campaigns and transactional emails is easy to use and allows a good range of customisation, effectively giving you the tools to get the design you are looking for.As this replaced hand writing our own emails, it has made things super quick compared to hand-rolled templates and I'd recommend it.
