What are some email marketing solutions available online?

Personally, I would recommend Convertkit.

It has far better deliverability than the likes of Get response or active campaign. In a study done in Sept 2020 by email tool tester Convertkit scored the highest with 96% Get response only got 86% and Active campaign was a low 73% This means more people will receive your emails with convertkit which should be your primary concern.

Beyond that, Convertkit offers a lot of fancy features which not only help me monetise my list but also save time. For example I can repurpose whole sequences of emails in different funnel without worrying that anyone will receive it twice - it recognises people who have received those emails and skips them straight past. I can also tag people in seconds from within the email builder (say if they click on a link and show interest in a topic) This means I can gather more info about my subscribers and deliver more targeted offers to them. You can achieve the same thing with most email platforms but it usually involves setting up complicated time-consuming workflows. No platform that i know of lets you do it in seconds from within the editor - amazing!

I have tried 4 different email platforms and have been very happy with convertkit.