.NET 2.0 SmtpClient , Failure Sending mail.

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.NET2.0

Hi Guys,

I'm using the .net SMTP classes to send emails out to clients,I've been using it for over 2 years without any problems.We have now switced over to a new email host and for some reason I get the following error when trying to send an email.

Failure sending mail.

System.FormatException: Invalid length for a Base-64 char array.
at System.Convert.FromBase64String(String s)
at System.Net.NTAuthentication.GetOutgoingBlob(String incomingBlob)
at System.Net.Mail.SmtpNtlmAuthenticationModule.Authenticate(String challenge, NetworkCredential credential, Object sessionCookie)

Any ideas what might be causing this problem ? I'm only parsing the host name,port number,username and password.All values are string except of course for the port which is an int.

Using Visual C# 2.0.

Thanks in advance for all help.

Posted 23-Nov-09 19:07pm

FJD.DEETLEFS

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Electr()n · Answer 1 · 2009-11-23T20:51:00

Solution 1

Hi

Does this problem persist everytime or only from time to time?

Posted 23-Nov-09 20:51pm

Electr()n

FJD.DEETLEFS · Answer 2 · 2009-11-23T21:09:00

Hey Guys,

I found a solution on the following link

http://blogs.msdn.com/knom/archive/2008/04/16/hacking-system-net-mail-smtpclient.aspx

Seems to be the underlaying authentication modules in the smtpClient that would be default use NTLM,by using reflection you can "override" the values.

// Example in specified link

FieldInfo transport = _client.GetType().GetField("transport", BindingFlags.NonPublic | BindingFlags.Instance); FieldInfo authModules = transport.GetValue(_client).GetType() .GetField("authenticationModules", BindingFlags.NonPublic | BindingFlags.Instance);

Array modulesArray = authModules.GetValue(transport.GetValue(_client)) as Array; modulesArray.SetValue(modulesArray.GetValue(2), 0); modulesArray.SetValue(modulesArray.GetValue(2), 1); modulesArray.SetValue(modulesArray.GetValue(2), 3);

In my code I did all the above,only difference is that I only replaced element number 1 in the array and made the value the same as the value in element 3 which would be "Login".This worked for me and I hope it will help someone else with the same problem that was not as lucky as to stumble on to the link.

// What I did in my code

modulesArray.SetValue(modulesArray.GetValue(3), 1);

Kind Regards,

FREDDIE.