Sparkpost (Symbiotic fork)

Symbiotic fork of the Sparkpost extension, with a few more features:

• CiviCRM "System Checks" to display alerts when there is a high bounce rate, and also display validated domains for the given API key (helpful for debugging).
• Bounce-tracking for transactional emails
• Sparkpost EU support
• Before sending emails, verify that the email is from a validated domain, to avoid fatal errors (useful for when sending emails from the Contact record - Send Email, and where an admin might have their Gmail address set as their "from", which will cause problems).
• Uses the Sparkpost PHP library for sending emails, rather than direct "curl". It seemed to improve performance at the time (your mileage may vary).

Also note that this fork does not create a webhook systematically. It has to be created manually (we hope to improve that, make it more clear). Symbiotic uses a single host as the recipient for webhooks, then re-routes to the appropriate site (using sparkpostrouter). We initially did this because Sparkpost sent webhook events to all sub-accounts, but this has since been fixed on their end. Nonetheless, we kept our central "router" because it made it easier to replay bounce events when there were problems, as well as keep more than 30 days of data.