How can i check smtp server without sending email? [duplicate]

Question

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Testing SMTP server is running via C# (5 answers)

Closed 5 years ago.

I had web application that users can set SMTP server information (server/host, SMTP Port, Username, Password, EmailAddress, usedSSL). i need when user set information validatre server without sending email and check Is smtp information valid or not?

I found website that works perfect and check is SMTP server alive (but not authentication check).. http://mxtoolbox.com/diagnostic.aspx

Edit 1:

Tanx @Dieter DHoker help me to find Testing SMTP server is running via C# in comments...

Is there anyway that i check authentication information (username & password & email address) as i need to check all smtp information is valid or not? that i asked before..

Answer 1

There's no username and password in SMTP (see rfc 821), so there's no way to test that. You could use a MAIL FROM and RCPT TO sequence, but not send any DATA, to see if you'll be allowed to send mail with the given information, without sending an actual mail.