Question Failure Sending Mail

[dhirendra]

Hello,
i have a scenario where i need to send some files present in a particular folder to separate email ids. i call by mail sending subrouting and pass the file location of 1 file at a time. i call this in a loop untill all the files are processed. each file is to be send to different or same users.
i am using the below code

Using email As New System.Net.Mail.MailMessage()
            Dim smtp_dtl As New System.Net.Mail.SmtpClient
            Dim attach_file As New System.Net.Mail.Attachment(filelocation)
            Dim email_from As New System.Net.Mail.MailAddress(from_names)
            email.Attachments.Add(attach_file)
            email.To.Add(to_names)
            email.From = email_from
            email.Subject = subject
            body = "Hi," & _
            vbCrLf & _
            "Please find attached " & reparray(rownum, 1).ToString & _
            " refreshed on " & repdate & vbCrLf & _
             vbCrLf & reparray(rownum, 6).ToString
            email.Body = body
            smtp_dtl.Host = My.Settings.smtpmain.ToString
            smtp_dtl.Port = 25
            'smtp_dtl.EnableSsl = True
            smtp_dtl.Timeout = 60
            smtp_dtl.UseDefaultCredentials = True
            smtp_dtl.Send(email)
        End Using

i am able to successfully send files if i provide valid email id in the field email.To .However if i add an invalid email id which doesnt exist say abc@xyz.com
then i get an error message "The operation has timed out"
which is perfectly fine.
however when processing files for which valid email id exists..then i get the error
Failure sending mail
when i restart my application and put valid email ids in the email.to
then everything works properly.

This issue may be probably due to the timeout=60 field. while i am able to send 1st file having valid email id, then 2 file with invalid id giving timed out error, now 3rd file with valid email id in :TO is giving failure sending mail.

Can any one suggest a proper way of tackling this issue.
how can i wait for the timeout to appear and then only get out of mailing sub.

 

[dhirendra]

Sorry for the post,
The timeout value was way too low 60millisec . i made it 20 seconds i.e 20000. i figured out that a value as low as 60milliseconds is too less to figure out if the TO address is a valid email id. i was receiving error " The operation has timeout" which is not correct. it should have been
Mailbox unavailable. The server response was: 3.4.5 Unable to relay for you@xyz.com
which i get now after increasing the timeout value.
Moved from CDO to SNM, where base time unit was seconds for specifying the timout.