Using Mailkit : "The SMTP server has unexpectedly disconnected."

Question

I am trying to use a free SMTP relay from SendGrid to send emails from my ASP.NET application. I can connect to the server, but when I try to authenticate, I get this error : "The SMTP server has unexpectedly disconnected."

using (var client = new SmtpClient())
        {
            client.ServerCertificateValidationCallback =
                (sender, certificate, certChainType, errors) => true;
            client.AuthenticationMechanisms.Remove("XOAUTH2");

            // connection
            client.Connect("smtp.host", 465, true);
            client.Authenticate("UserName", "Password");//error occurs here

            client.Send(email);
            client.Disconnect(true);
        }

Once again, I can connect without any problem, but when I try to authenticate, I get the previously mentionned error...

Any suggestions?

Cheers

https://sendgrid.com/docs/for-developers/sending-email/v2-csharp-code-example/ — mjwills, Aug 27 '19 at 14:20
That's not quite what I need since I'm using Mailkit. I'm starting to think that maybe SendGrid isn't the most appropriate service for what I'm trying to do. — jabir saidi, Aug 27 '19 at 14:35

score 3 · Answer 1 · answered Dec 17 '19 at 14:32

3

You have to supply:

Username: is apikey (as a hard-coded value 'apikey').
Password: is the apikey you generated from the web, which is a big hashy-like string.

You can find this on their docs. But it was hard to find.

answered Dec 17 '19 at 14:32

EzLo

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And unlike the Telnet example on their site you *don't* need to Base64 encode either username or API key. – Alan B Apr 21 '21 at 13:57

jabir saidi · Accepted Answer · 2019-09-05T20:13:36.567

1

I solved my issue changing from SendGrid to gooogle's free SMTP service for all of their users. Simply follow the steps here and you should be good to go!

edited Sep 05 '19 at 20:13

answered Aug 27 '19 at 16:12

jabir saidi

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Using Mailkit : "The SMTP server has unexpectedly disconnected."

2 Answers2