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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: <name@domain.tld> Relay access denied

Any feedback would be appriciated.

Regards and happy coding, Thomas

Muleskinner
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  • update: when I do a smtp:195.69.129.85 on mxtoolbox.com I get: Warning - Reverse DNS does not match SMTP Banner and 554 5.7.1 : Recipient address rejected: Access denied [172 ms] Is this normal? – Muleskinner May 19 '10 at 11:43
  • Server issue, nothing to do with .NET. – leppie Jul 31 '12 at 12:56
  • Did you find solution for resolve this problem? I have the same situation. – Smit Nov 13 '12 at 08:42

3 Answers3

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"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.

Alex K.
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  • thank you for your input, but how can this explain that messages, with same sender, same reciever and (almost) same content sometimes are recieved successfully and sometimes not? – Muleskinner May 19 '10 at 11:35
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server which trying to relay message requires authentication from the mail which SMTP sent.So try to use domain credentials to send mail.

karthickpradhaban
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SMTP server can be configured to reject your requests under high load.

Der_Meister
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