
API for free email forwarding service.
ImprovMX API is a free Email API that requires apiKey authentication, is served over HTTPS and has unconfirmed CORS support.
Complete REST API documentation for programmatically managing your ImprovMX email forwarding domains and aliases.
Details from improvmx.com.

Unified API suite · now live
Geocode an address, validate an email, track a flight or pull stock data with one account, one dashboard and one API key.
Validate email addresses
Validate email syntax and MX, detect disposable/role addresses, suggest typo fixes
Free email validation: MX check, disposable detection, syntax
The ImprovMX API is provided by ImprovMX (improvmx.com). Complete REST API documentation for programmatically managing your ImprovMX email forwarding domains and aliases.
Yes. The ImprovMX API is listed in the Email category of the public-apis directory, which only includes APIs that are free or have a free tier. Check its documentation for rate limits and paid plans.
Yes. The ImprovMX API uses apiKey authentication, so you need to register for credentials before making requests.
CORS support for the ImprovMX API is unknown. Test a request from the browser, and fall back to a server-side call if it is blocked.
Yes. The ImprovMX API is served over HTTPS, so it's safe to use in production.