The best feature that we use right out of the box is the dynamic templates feature and the ability to create a dynamic template from scratch by using HTML code or by using any of the templates from the design library, which makes it very easy to build emails right out of the box with custom parameters that can be passed based on each different user that the same email is going to be sent out to. The second best feature would probably be the activity feed and the email logs that are maintained properly, which shows us when a particular email was sent out, when it got delivered, and when the user opened the email.
SendGrid also provides the option to create unsubscribe groups, which we set to particular communications so that it won't be spamming people who are not in need of that communication. Users can opt themselves into the subscription or un-subscription group, and they would be automatically excluded.
We are now able to handle multiple different emails which still belong to the same SMTP because we would ideally be handling everything in a single inbox, but the emails that get sent out would be specific from different brands. For example, a student that is currently enrolled for education subjects would get an email from education@thedomain.com versus a student which is enrolled for a particular UCAT course would be getting an email from ucat@thedomain.com. In that way, we are able to send out emails to multiple people, and the from address can be the same SMTP but different labels or domain names, which helps create a more professional view for the end user.
Primarily, the best item that has impacted us is the dynamic templates feature, which helps us create a particular template using HTML and CSS along with certain parameters so that we are able to send out the same structured email to multiple different students but with different data points.