Yahoo email account not open after i write this code in c#

Question

Hi guys i make send email by this code 
but after one week the yahoo account  not open why 
the yahoo account not open is [email protected]
and this is my code 
string smtpAddress = "smtp.mail.yahoo.com";int portNumber = 587;
bool enableSSL = true;
string emailFrom = "[email protected]";
string password = "passw#rd";
string emailTo = "[email protected]";
string subject = "Working Finish today" + label6.Text;
string body = "Summary for Date" + "" + label6.Text + "" +
"Quantity Required" + "" + "(" + label17.Text + ")" + "/" +
"Quantity Shipped""/" + "(" + label18.Text + ")" + "/" +
"Quantity Remaining" + "/" + "(" + label19.Text + ")";
using (MailMessage mail = new MailMessage())
mail.From = new MailAddress(emailFrom);
mail.To.Add(emailTo);
mail.Subject = subject;
mail.Body = body;
mail.IsBodyHtml = true;
mail.Attachments.Add(new Attachment("I:\\gridview" + DateTime.Today.ToString("dd-MM-yyyy") + ".csv"));
System.Net.Mail.SmtpClient smtp = new SmtpClient(smtpAddress, portNumber);
smtp.Credentials = new NetworkCredential(emailFrom, password);
smtp.EnableSsl = enableSSL;
smtp.Send(mail);
What is wrong in this code 
I create account by yahoo two times 
and after this open may be 6 days and after this not open
and cannot open your yahoo account after this i try from another computer but not open
i check caps lock and every thing and language and i write in files before i open 
but not accept to open
Why 

Answer 1

@ahmedsalah2012
>>IF problem is limitation How i now the limitation finish or still exist
I've just do a quick search. Please refer  to
http://group-mail.com/sending-email/email-sending-limits-for-isp-web-hosting-and-free-email-providers/
For more information about the options available to send more email than allowed by your current outgoing SMTP mail server, read
Email Send Limits and Options.
Based on your scenario, your Email is Yahoo, please also consider to post in Yahoo official website for more specific response.
Note: This response contains a reference to a third party World Wide Web site. Microsoft is providing this information as a convenience
to you. 
Microsoft does not control these sites and has not tested any software or information found on these sites;Therefore, Microsoft
cannot make any representations regarding the quality, safety, or suitability of any software or information found there.
There are inherent dangers in the use of any software found on the Internet, and Microsoft cautions you to make sure that you
completely understand the risk before retrieving any software from the Internet.
Best regards,
Kristin
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