Sendgrid is software that I set up for your website to make sure that email is being delivered.
For example, if your website accepts transactions or hosts forms, we'll want to use Sendgrid to make sure that any notifications, receipts, confirmations, etc... are completed.
Your website is set up to send emails when someone buys a product, or notifications when someone fills out a form on your site. By default, WordPress software will do this, but it's not always reliable because we can't track the messages or troubleshoot as easily. Sendgrid allows us to see how many messages were sent, whether it was opened, etc... just like any email service provider does. Therefore, by using Sendgrid we're making your website have the functionality you would expect from ConvertKit or Mailchimp.
For more information about SendGrid, visit their website sendgrid.co