Why the ConvertKit emailing service is better than services like Mailchimp is because it allows you to segment your email list when you send them emails and it will not double count the number of subscribers. The result is that you will pay far less as your list grows. In addition, it also has a lot more functionality than Mailchimp.
Another thing to consider if you are going with Mailchimp is that they don’t like any sort of affiliate content. If you are sending out a link to a blog post that has any sort of affiliate link, you are violating their terms of service and will delete your account. All the time and effort you spend building up this asset will be lost, so choose carefully.
If you want even more functionality you can go with Infusionsoft, it’s a monster and overkill for a lot of smaller businesses.
Note: Never send emails to big lists of people from your own domain name and email account as this can get your account banned for spam. When someone reports your email as spam, they will blacklist your IP address. Using one of these services will mean that your emails will be sent from their whitelisted servers.
Here are some training videos that will help you make the most of your Convertkit tool.