Asp.net 2.0 strange problems with SMTP operations

The new system that was upgraded yesterday has discovered another problem today:

In the whole system, all the places where the mail is to be sent, when the mail is sent, all errors are reported! But in fact, the mail has been successfully sent and recorded in the database.

[Because the system is upgraded, the previous system was developed with vs2005 beta1 and is now in the official version. SourceProgram, Do not make much changes, just put the system. web. mail. change smtpserver to system. net. mail. smtpclient thought there should be no error, because it could not build an SMTP environment, so there was no test, and it was just a bit boring...]

Debug program, found in the client. Send, throw an exception: non-secure connection, need to verify.
We do need to verify the SMTP server. I know this, but the problem is: why do we not need to verify the program previously written with beta1, and no error is reported, and sent successfully?

You can't explain it! Check again tomorrow.