Identify your target market. Who will be receiving your mailing? Are you contacting past customers, current prospects or sending a cold mail from a bought mailing list? If you plan to buy a list, do your research before spending any money to make sure it's an updated and quality list. Further, follow the list owner's rules for mailing. For example, most only "rent" you the names for one one mailing. The only way to add list members to your permanent list is if they respond to your mailing.
InfusionSoft is a fully functional CRM and marketing solution created for small and medium size businesses. Comparing it to MailChimp or AWeber is like comparing a Lamborghini to a VW Golf. It provides highly advanced features for list segmentation, lead scoring and marketing automation. On top of all that, you can integrate all of these features with your optin form using Infusionsoft Tags + OptinMonster.