Triggered email marketing campaigns are the best channel to engage leads and existing clients. They routinely have the best conversion rates and don't cost you a cent in media. When set up correctly you could be looking at conversion rates above 15% and the impact on your client retention rates can be unbelievable.
Once these campaigns are set up you'll need to keep an eye on them to make sure they continue to convert and continue to improve. You can do this by running tests and optimising them. These changes are often easy and I can show you how to make some of these changes as a bonus.
If you're not already running these campaigns then you need to start ASAP!