I am on iis6 and mojoportal 2.3.0.10

The website used to send email successfully; now it does not work anymore

From the log:

2009-07-03 15:07:30,988 ERROR mojoPortal.Net.Email - error sending email to xxx, message was: xxx

System.Net.Mail.SmtpException: Failure sending mail. ---> System.NullReferenceException: Object reference not set to an instance of an object.
at System.Net.Mail.SmtpConnection.GetConnection(String host, Int32 port)
at System.Net.Mail.SmtpTransport.GetConnection(String host, Int32 port)
at System.Net.Mail.SmtpClient.GetConnection()
at System.Net.Mail.SmtpClient.Send(MailMessage message)
--- End of inner exception stack trace ---
at System.Net.Mail.SmtpClient.Send(MailMessage message)
at mojoPortal.Net.Email.SendEmailNormal(SmtpSettings smtpSettings, String from, String replyTo, String to, String cc, String bcc, String subject, String messageBody, Boolean html, String priority, String[] attachmentPaths, String[] attachmentNames)

My website used to be configured as localhost:25; unauthenticated as I ip banned all the address except localhost

my own asp code is perfectly working with my mail server configuration and system.net.mail

and, i have other 4 mojoportal 2.3.0.4 installations that are working fine on sending email (but, this is kinda obvious, as is used dotnetopenmail)

note for joe: i deleted the other post, sorry, i thought it was related, then when i read again, i saw the problem does not write an error in the log, so it is a different problem

How i can copy the stack trace?

Solved:

it seems that the email function ignores the "SMTP requires authentication" checkbox

Even if i leave it unchecked, when I enter my smtp user&password, the emails will be sent