Use the If Viewed Specific Email trigger to follow-up from another email at an ideal time, after contacts show interest by viewing it.

Example

Send an email campaign to contacts who have shown interest by viewing your “Investment Opportunities” email, with an invite to an upcoming Investment seminar. *

After setting your recipients:

• Add a new module and choose the trigger of Viewed Email.
  • Within the module, select the email you want to follow up on, e.g.: "Investment Opportunities".
• Optionally, add a delay between the selected email being viewed and your follow up, by choosing add a new module, and Delay.
  • Select a delay period, e.g.: 1 day
• Add a new module and choose Send Email.
  • Within the module, select your follow up email, e.g.: "Investment Seminar"
• Once all your selections are made, select Save, or Save & Activate.

* You could alternatively use the Viewed Email condition