0

I'm trying to send emails via smtp.gmail.com in the standard way, and I'm getting a standard error, but for some non-standard reason.

Specifically, I get this error: System.Net.Mail.SmtpException: The SMTP server requires a secure connection or the client was not authenticated. The server response was: 5.5.1 Authentication Required. when I send the mail.

The answers on this link have not helped me: The SMTP server requires a secure connection or the client was not authenticated. The server response was: 5.5.1 Authentication Required?

I suspect that there are additional steps required if you're trying to do this from a custom domain.

I've created a throw-away standard Gmail account to test out my code and everything works perfectly there.

  • If I en-/dis-able Less Secure Apps then it behaves as you'd expect, and as per the linked solutions.

  • If I en-/dis-able 2FA and create 3rd party app passwords then, again, it behaves as I'd expect, and as per the linked solutions.

So my code, and my ability to configure a general Gamil acccount, are working just fine.

But when I use an otherwise identical GSuite email address, set up on a custom domain (system@clientdomain.co.uk) then nothing works :( I've tried all the permutations, with/without LessSecureApps, with main user password / with 3rd Party App Password, etc. Nothing works.

I can only assume that either the custom domain or the fact that it's a GSuite account is breaking it.

What now?

Brondahl
  • 7,402
  • 5
  • 45
  • 74

1 Answers1

0

So apparently I either needed to wait longer, or change the settings harder!!

A colleague wandered past and asked what the problem was and I demonstrated it, including going through and setting the settings again, and this time it worked. I'm 80% sure they were the same settings, but perhaps not?

Brondahl
  • 7,402
  • 5
  • 45
  • 74