I am trying to send Email on my yahoo account "firstname.lastname@example.org" using "smtp.mail.yahoo.com" as SMTP server. But its giving me an error "Error 16502 occurred at 502 Command not implemented" i am sending this email by using "SMTP email send message.vi" Please tell me the solution.
That library does not support encrypted authentification so only supports the HELO SMTP command. Since Yahoo most likely requires encrypted authentification it probably has removed the HELO command entirely from it's known command vocabulary and only reacts to the EHLO, which the SMTP Email VIs don't know and aren't that easy to implement either.
Look for other solutions on this forum, most of them using ActiveX or .Net instead.