Relay access denied, system.net.mail

.net smtp email asp.net system.net.mail
Muleskinner picture Muleskinner · May 19, 2010 · Viewed 12.1k times · Source

We have a aspx.net site which send out mail to users using a web server hosted externly.

This have been working perfectly for a couple of years sending 100-1000 mails pr day, but recently users have started to report that they do not recieve mails - some days they recieve all mails (2-100) and some days only 40-60%.

All mails are formatted equal and have the same content (except for some dynamic fields like name, password etc).

I've looked at my error log and now I see this error when mails are lost:

system.net.mail.smtpexception: transaction failed the server response was: <[email protected]> Relay access denied

Any feedback would be appriciated.

Regards and happy coding, Thomas

Answer

Alex K. picture Alex K. · May 19, 2010

"Relay access denied" is usually caused either because the mail server doesn't recognize the domain.tld domain in the senders address so wont send mail on their behalf, or because the server requires SMTP authentication which was not provided.

Related questions

Sending email in .NET through Gmail

Instead of relying on my host to send an email, I was thinking of sending the email messages using my Gmail account. The emails are personalized emails to the bands I play on my show. Is it possible to do …

Read More
Sending email through Gmail SMTP server with C#

For some reason neither the accepted answer nor any others work for me for "Sending email in .NET through Gmail". Why would they not work? UPDATE: I have tried all the answers (accepted and otherwise) in the other question, but …

Read More
How can I send emails through SSL SMTP with the .NET Framework?

Is there a way with the .NET Framework to send emails through an SSL SMTP server on port 465? The usual way: System.Net.Mail.SmtpClient _SmtpServer = new System.Net.Mail.SmtpClient("tempurl.org"); _SmtpServer.Port = 465; _SmtpServer.EnableSsl = true; _SmtpServer.Credentials = …

Read More