About a month ago, a spammer exploited a feature we have in Savio to send 20,000 spam emails.
It's not a ton of spam emails, but it meant 43.7% of emails sent by Savio (including emails from our customers to their customers) was ending up in spam folders.
These are the steps we took to improve our app's email deliverability and reduce the percentage of emails being flagged as spam from 43.7% to 1.4%:
https://www.savio.io/blog/improving-email-deliverability-from-43-percent-spam-to-1-percent/