System.Web.Mail FAQ

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4.3.6 The specified protocol is unknown. Printer Friendly   Email This FAQ   Discuss

This is probably a relay error. Make sure you can relay through the SmtpMail.SmtpServer either by your IP address, by your MailMessage.From address, or if you need to authenticate, check out 3.8 How do I authenticate to send an email?
If SmtpMail.SmtpServer is set to "" or "localhost", and you are using the built in IIS SMTP Service, you can allow relaying for by
  • Opening the IIS Admin MMC
  • Right-Clicking on the SMTP Virtual Server and selecting Properties
  • On the Access tab, click the Relay button
  • Grant (or the IP address used by System.Web.Mail) to the Computers list.
  • Close all dialogs
  • Restarting the SMTP Service
Also, be sure to check the InnerException for any additional, helpful information.

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