Mandrill is an email infrastructure service offered as an add-on for Mailchimp that you can use to send email notifications.
Once you have set up a Mandrill account:
Create a Domain
Log in to your Mandrill account.
Click the Settings tab from the left side navigation menu.
Click the Domains tab from the top navigation bar.
Click Set up your sending domain button. Add the domain from which you wish to send emails. Click the Add button.
You can view your current added domain in the Domain Details. Verify your Domain by clicking Verify a Domain button on the right side.
Create API Key and Obtain Other Details:
In the Settings section, click New API Key button to create API Key.
Add a description of your API Key and click on the Create API Key button to generate your API Key.
After successful API Key creation, you will be able to see:
Host
Port
SMTP Username: enter it in the Login field at TurnKey Lender Email notifications integration settings
SMTP Password: enter it in the Login field at TurnKey Lender Email notifications integration settings