Sparkpost SMTP

Looking on Stackoverflow and Google for this error it seems that the issue could be in the user name and password. That means that you have to use an existing mail account at the SMTP server (your client domain mail id), connect to the server using an authentication method, and send the password for your account.

Thanks for the quick response. I have tested 3 different API keys (passwords) on other applications and it works without error. It just seems to be an issue using this with Kentico.

Refer the following links -

https://www.sparkpost.com/docs/user-guide/unconfigured-sending-domain/

https://www.sparkpost.com/docs/faq/relaying-denied-error/

https://www.sparkpost.com/docs/integrations/postfix/

Thanks, Vasu but non of this helps.

https://www.sparkpost.com/docs/user-guide/unconfigured-sending-domain/ As mentioned the same details work on other software applications. It is only on Kentico I have an issue sending mail with this error.

https://www.sparkpost.com/docs/faq/relaying-denied-error/ Kentico only allows you to specify server, user, password and a check box for SSL. There is no separate field for port number, but I have tried appending both 587 and 2525 to the server name with no success.

https://www.sparkpost.com/docs/integrations/postfix/ This is not relevant