What type of autoresponder should I choose in Freshmail?

Which type of Freshmail autoresponder should I use to send a series of different emails to users who have subscribed to my website opt-in and opened the initial welcome email? I read in the Freshmail help pages that I should use the “Open autoresponder” first, followed by the “Follow-up autoresponder”, but I am not sure if I understood this correctly. Thank you for your help.

To send a series of different emails to users who have subscribed to your website opt-in and opened the initial welcome email in Freshmail, you should use the “Follow-up autoresponder”. The first “Follow-up” message should have the sign-up email as a “basic autoresponder”. In the following messages, each one should have the previous email as a basic autoresponder. The “Open autoresponder” is not necessary for this sequence. However, if you are interested in self-hosted autoresponders, you can do some research as it may require technical skills and could have associated costs.