diff --git a/README.md b/README.md
index f455e319..81a7cd35 100644
--- a/README.md
+++ b/README.md
@@ -377,6 +377,7 @@ Table of Contents
   * [migadu.com](https://www.migadu.com/) — Email Hosting (Webmail, SMTP, IMAP, ...) — free plan is limited to 10 outgoing mails/day
   * [socketlabs.com](https://www.socketlabs.com) - 40k emails free for first month, then first 2000 emails/month free
   * [postmarkapp.com](https://postmarkapp.com/) - 100 emails/month free, unlimited DMARC weekly digests
+  * [testmail.app](https://testmail.app/) - Automate end-to-end email tests with unlimited mailboxes and a GraphQL API. 100 emails/month free forever, unlimited free for open source.
 
 ## CDN and Protection