Having a custom 'thank you' or completion page for someone after they sign up for your newsletter or email list is important for two reasons:
- User experience. You can have a nice message thanking them and outlining what they can expect (check their inbox to confirm, how frequently you'll email them, what your content will focus on, etc.) and have a soft ask for a next action (make a donation, follow on social media, etc.).
- Tracking. The easiest way to track email signups as 'conversions' in Google Analytics is to set them up as a goal. These can then get imported into your AdWords account as a Conversion and tracked there as well.
Read more about 'thank you' pages and a good example here.
So it's important! MailChimp also makes it really easy. Here's what you need to do:
- Sign into your account
- Select the list that you want people to sign up to
- Navigate to the 'Singup forms' section and select "General form'
- From the drop down find the "Signup thank you page'
- Copy your 'custom' thank you page URL and paste it in the form under 'Instead of showing this thank you page, send subscribers to another URL
- Click Save
Here's a GIF showing you as well.