"Unrecognized authentication type" when calling UseBestLogin

Question

Limilabs.Client.SMTP.SmtpResponseException: Unrecognized authentication type
   at Limilabs.Client.SMTP.Smtp. (String user, String password)
   at Limilabs.Client.SMTP.Smtp.UseBestLogin(String user, String password)
   at EmailReceiver.EmailProcessor.SendMessage(EmailInboxSettings settings, IList`1 recipients, String subject, String body)

What are possible causes and solutions?

thanks

Answer 1

1) There is a good chance your SMTP server doesn't require authentication at all.
Simply comment-out the UseBestLogin line and check.

client.Connect("mail.example.com");
// client.UseBestLogin("user", "pass");

2) Make sure you use default port for submitting emails (587) not port 25.
Use Connect method without specifying port.

client.Connect("mail.example.com");
client.UseBestLogin("user", "pass");

3) Try using SSL (ConnectSSL):

client.ConnectSSL("mail.example.com");
client.UseBestLogin("user", "pass");

4) Turn on logging:
https://www.limilabs.com/blog/logging-in-mail-dll