The most effective way to communicate with your new email leads is by using an email autoresponder. This allows you to write emails in advance so you can set it and forget it. The money is in the follow up after all.
I recommend 3 affiliate friendly autoresponders in MailingBoss, AWeber and GetResponse. I would absolutely stay away from MailChimp because they do not allow affiliate campaigns and your account will get shutdown.
This is my #1 recommendation. It's part of the Builderall Platform which allows you to build websites, sales funnels, landing pages and much more. It also lets you store up to 10,000 email leads for only $29.90/month.
If you already have a website and don't need the bells and whistles of Builderall, GetResponse is the way to go. It's quite affordable compared to other autoresponders. For only $12.30/month you can store 1,000 email leads.
AWeber is extremely affiliate friendly. They have a great reputation among affiliate marketers. They cost a bit more but is well wort the extra money. You can store up to 500 email leads for $19/month.