[c# form] SMTP server verification?

[piercy]

is there a way to verify a SMTP server?

for instance.
my users specify the SMTP server depending on there local settings.
if they put in a wrong smtp address it will still attempt to send the email and wont display a fail.

is there anyway to verify the server is a smtp server?
or any other methods of verification i can take to check this?

in basic a way of saying
"hello server, do you have SMTP?"
"No."
;) haha

Thanks in advance,
Piercy

[JamieHowarth0]

Hi Piercy,

I am a complete n00b on C# but I think this might help you:

http://www.jscape.com/articles/telnet_using_csharp.html

I understand that you may not want to fork out on a third-party API/ActiveX object for a single function, but I figure that if you can create a telnet object in C# using the .NET Framework, and then telnet to the port 25 of the server requested, then do an EHLO command ("do you send mail?" lol). If you get a response, great, send the mail through. If not, kick your user to find a decent server lol.

Hope it helps!

medicineworker

[JamieHowarth0]

This might also come in useful:

https://forums.microsoft.com/MSDN/ShowPost.aspx?PostID=540202&SiteID=1

There's also a link on there to a C# class that you can download and then use it's methods to create a telnet session.

[piercy]

thanks very much for your help. fairly easy to implement. found this class file
http://www.c-sharpcorner.com/uploadfile/tylerkline/telnetscripting11282005001158am/telnetscripting.aspx

didnt really need to use the EHLO command. the fact that it connects to port 25 is enough proof a SMTP server exists.

so for this class file i just did

if(telnet.Connect())
{
// do summit
}
else
{
//display error
}
 

Thanks for your help :)