Sparkpost reported an elevated level of API errors and latency APIs for some US customers on 28 Nov 2018 20:30 - 21:44 UTC.
If you got any errors while sending emails during issue time-frame, please try again.
Note: This issue does not impact our Sparkpost Enterprise customers hosted in the EU.
More details on Sparkpost status page: https://status.sparkpost.com/incidents/h27bwxyy4gy2
Resolved: Sparkpost reported that issue was resolved on 28 Nov 2018 21:44 UTC