SMTP SASL SASL AUTH OAUTH2 SASL-IR RFC4954 RFC6749 # Server-side AUTH XOAUTH2 REPLY AUTH 235 Authenticated # Client-side smtp SMTP OAuth 2.0 (XOAUTH2) authentication with initial response mail body smtp://%HOSTIP:%SMTPPORT/%TESTNUMBER --mail-rcpt recipient@example.com --mail-from sender@example.com -u user --oauth2-bearer mF_9.B5f-4.1JqM --sasl-ir -T - # Verify data after the test has been "shot" EHLO %TESTNUMBER AUTH XOAUTH2 %b64[user=user%01auth=Bearer mF_9.B5f-4.1JqM%01%01]b64% MAIL FROM:%LTsender@example.com%GT RCPT TO:%LTrecipient@example.com%GT DATA QUIT mail body .