4 ms·

I have my email with Fastmail too and issuing a RCPT TO command via telnet returns the following: > 451 4.7.1 <marcus@utf9k.net>: Recipient address rejected: T

• X-Cubed 5y ago
  The library identifies itself to the mail server with a from address of "testing@example.com". It's probably a good idea to use an email address you own as the from address if you want to use this in production, eg: "testing@mycorp.com", to avoid this grey-listing.
  • mkl 5y ago
    Indeed: { "input": "testing@example.com", "is_reachable": "unknown", ... }