Yandex mail problem

[Bozuyla]

Hi guys
I have used a Yandex mail account in my project to send mail. I have taken an error for 10 days. The error message is "554 Error: send AUTH command first. 17082980431EZcQL1n9Gk0TJtvpGYN". Why do I take this message although I didn't make any changes in my code?

Thanks...

 

[Skydiver]

I've not kept up with email technologies and protocols, but I heard about some protocols been deprecated recently, and some new requirements for authentication and security. Sorry, for the handwaving, but I didn't dig into the details of it because I'm burnt out on email. It looks like your email provider has instituted those new authentication requirements.

 

[Skydiver]

Moving thread since this isn't a WinForms issue...

 

[Skydiver]

Can you show us this code that you have not touched? Is it using the built in .NET Framework SmtpClient class or did you roll your own version of that class?