smtpclient failure sending mail

Question

here is my code for int i   0  i  lt  number   i          MailAddress to   new MailAddress iMail to       MailAddress from   new MailAddress iMail from  iMail displayName       string body   iMail body      string subject   iMail sub      oMail   new MailMessage from  to       oMail Subject   subject      oMail Body   body      oMail IsBodyHtml   true      oMail Priority   MailPriority Normal      oMail Sender   from      s   new SmtpClient smtpServer       if  s    null                s Send oMail             oMail Dispose        s   null     this loops sends over 60 000 email  but my problem i am getting  quot  failure sending  mail quot  in some of the email some times 5000 and some time less then that rest of them gets delivered  and i have check all those error out email has valid email address  dont know what is the problem  i really need help in this  Edit  This is my exception Trace  Error - Failure sending mail   Inner Ex - System IO IOException  Unable to read data from the transport connection  net io connectionclosed  at System Net Mail SmtpReplyReaderFactory ProcessRead Byte   buffer  Int32 offset  Int32 read  Boolean readLine  at System Net Mail SmtpReplyReaderFactory ReadLines SmtpReplyReader caller  Boolean oneLine  at System Net Mail SmtpReplyReaderFactory ReadLine SmtpReplyReader caller  at System Net Mail CheckCommand Send SmtpConnection conn  String amp  response  at System Net Mail MailCommand Send SmtpConnection conn  Byte   command  String from  at System Net Mail SmtpTransport SendMail MailAddress sender  MailAddressCollection recipients  String deliveryNotify  SmtpFailedRecipientException amp  exception

User · Answer

I experienced the same issue when sending high volume email  Setting the deliveryMethod property to PickupDirectoryFromIis fixed it for me  Also don t create a new SmtpClient everytime

User · Answer

Five years later   I hope this developer isn t still waiting for a fix to this     I had the same issue  caused by the same error  I was declaring the SmtpClient inside the loop     The fix is simple - declare it once  outside the loop     MailAddress mail   null  SmtpClient client   new SmtpClient    client Port   25  client EnableSsl   false  client DeliveryMethod   SmtpDeliveryMethod Network  client UseDefaultCredentials   true  client Host   smtpAddress            Enter your company s email server here   for int i   0  i  lt  number   i          mail   new MailMessage iMail from  iMail to       mail Subject   iMail sub      mail Body   iMail body      mail IsBodyHtml   true      mail Priority   MailPriority Normal      mail Sender   from      client Send mail     mail Dispose    client Dispose

User · Answer

Well  the  failure sending e-mail  should hopefully have a bit more detail   But there are a few things that could cause this    Restrictions on the  From  address   If you are using different from addresses  some could be blocked by your SMTP service from being able to send  Flood prevention on your SMTP service could be stopping the e-mails from going out    Regardless if it is one of these or another error  you will want to look at the exception and inner exception to get a bit more detail

User · Answer

This error can appear when the web server can t access the mail server  Make sure the web server can reach the mail server  for instance pinging it

User · Answer

what error do you get is it a SmtpFailedrecipientException  if so you can check the innerexceptions list and view the StatusCode to get more information  the link below has some good information  MSDN  Edit for the new information  Thisis a problem with finding your SMTP server from what I can see  though you say that it only happens on some emails  Are you using more than one smtp server and if so maybe you can tract the issue down to one in particular  if not it may be that the speed amount of emails you are sending is causing your smtp server some issue

User · Answer

apparently this problem got solved just by increasing queue size on my 3rd party smtp server  but  the answer by Nip sounds like it is fairly usefull too

User · Answer

For us  everything was fine  emails are very small and not a lot of them are sent and sudently it gave this error   It appeared that a technicien installed ASTARO which was preventing email to be sent   and we were getting this error so yes the error is a bit cryptic but I hope this could help others

User · Answer

Seeing your loop for sending emails and the error which you provided there is only solution  Declare the mail object out of the loop and assign fromaddress out of the loop which you are using for sending mails  The fromaddress field is getting assigned again and again in the loop that is your problem

[c#] smtpclient " failure sending mail"

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