'Error 535 - sending SMTP Email to SendGrid using Telnet
I'm trying to send an SMTP Email to SendGrid using Telnet and getting "535 Authentication failed: The provided authorization grant is invalid, expired, or revoked" as a response when I enter my base64 encoded API Key.
I have authenticated my domain. I have a Full Access SendGrid API Key (and converted it to base64).
I have created and verified a sender (but, it has a mere [email protected] address).
I am following the steps at https://docs.sendgrid.com/for-developers/sending-email/getting-started-smtp. I have tried port 25 and port 587, but I can't get beyond step 4: Enter your Base64 converted API Key.
What could be causing this error? Do I need to create a sender with a business email address? Do I need a paid SendGrid plan?
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