Summary
addy.io has passed an independent security audit conducted by Securitum. The audit included a web application penetration test and a source code audit. No significant vulnerabilities were identified during testing, and the 2 low-risk issues that were found have been fixed.
Full report: https://addy.io/addy-io-security-audit.pdf
Looks interesting, but I’d be too afraid of the service going under in the future.