Imo it is the best form of marketing - someone is expressing their interest in a certain area and so much so they are happy to give you their email so you can further educate them - with a large list, and some trust this will be your best asset.
email marketing is the best way for promoting because can make many sale in one day My suggestion is use aweber good luck
I certainly wouldn't want to try to promote Clickbank products without autoresponder emails to go out to my opted-in list for each niche: that would probably be leaving three quarters of the money on the table. You can get occasional sales without that, it's true, if your keyword-targetting and landing-page are good enough, but the overwhelming majority of the income is in the email follow-up.