SMTP SASL SASL AUTH PLAIN connection reuse RFC4616 RFC4954 # Server-side AUTH PLAIN REPLY AUTH 334 PLAIN supported REPLY %b64[user.one%00user.one%00secret]b64% 235 Authenticated REPLY %b64[user.two%00user.two%00secret]b64% 235 Authenticated # Client-side smtp SMTP multiple connection authentication mail body smtp://%HOSTIP:%SMTPPORT/%TESTNUMBER001 --mail-rcpt recipient@example.com --mail-from sender@example.com -u user.one:secret -T %LOGDIR/upload%TESTNUMBER -: smtp://%HOSTIP:%SMTPPORT/%TESTNUMBER002 --mail-rcpt recipient@example.com --mail-from sender@example.com -u user.two:secret -T %LOGDIR/upload%TESTNUMBER # Verify data after the test has been "shot" EHLO %TESTNUMBER001 AUTH PLAIN %b64[user.one%00user.one%00secret]b64% MAIL FROM:%LTsender@example.com%GT RCPT TO:%LTrecipient@example.com%GT DATA QUIT EHLO %TESTNUMBER002 AUTH PLAIN %b64[user.two%00user.two%00secret]b64% MAIL FROM:%LTsender@example.com%GT RCPT TO:%LTrecipient@example.com%GT DATA QUIT mail body .