OptimizePress has a lot of email marketing service integrations, however there are a few that we still do not have an API level integration for.
To get around this, you could use Zapier along with the Zapier Email Parser to add leads to your lists.
Here is what you would need to do:
1) Go to Zapier.com and either login or create a new account.
2) Click one of the links further down on this page for the service you want to use (Drip, MadMimi, etc..)
3) When adding an Opt-in form to your page in OptimizePress, select the "Email Data" option. Use the email address that Zapier gives you, and then the data from that form will go to Zapier. You will need to do this at least once so the email parser in Zapier has some data to work with that you can setup the zap with.
4) Finally, create the zap to map the data from the email parser into your email marketing service to create a contact.
Here are some links to some guides on Zapier that will help:
Using Drip with Zapier: https://zapier.com/zapbook/zaps/453/parse-emails-into-drip-for-easy-drip-campaigns/
Using MadMimi With Zapier: https://zapier.com/zapbook/zaps/6278/add-new-mad-mimi-audience-members-for-new-parsed-emails/
You can use ANY App in Zapier to import this data, it is not limited to just the 2 mentioned above (not all of the apps have guides for using the email parser).
Here are more guides from Zapier on using the email parser:
Add contacts to Salesforce: https://zapier.com/zapbook/zaps/3122/add-contacts-from-zapier-email-parser-emails-as-salesforce-contacts/
Add contacts to Agile CRM: https://zapier.com/zapbook/zaps/3990/create-agile-crm-contacts-from-parsed-emails/
Add contacts to Sugar CRM: https://zapier.com/zapbook/zaps/3052/add-new-email-parser-emails-as-sugarcrm-leads/
Add contacts to Hubspot: https://zapier.com/zapbook/zaps/4656/create-or-update-hubspot-contacts-from-parsed-incoming-emails/
It should be noted that our support team are not able to help setup zaps or the email parser in Zapier. If you have any questions about how to use Zapier, or the email parser we would suggest reaching out to Zapier support.