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Error: Failing sending email: LocalErrorInProcessing.: System.Net (https://System.Net) (https://System.Net) .Mail.SmtpException: Error in processing. The server response was: Open relay not allowed

Issue

When attempting to send an email, the following error is logged in the ULS logs:
 
Failing sending email: LocalErrorInProcessing.: System.Net (https://System.Net) (system is for sale at Squadhelp.com!) .Mail.SmtpException: Error in processing. The server response was: Open relay not allowed

- Customer Community 

at System.Net (system is for sale at Squadhelp.com!) (system is for sale at Squadhelp.com!) .Mail.RecipientCommand.CheckResponse(SmtpStatusCode statusCode, String response) at System.Net (system is for sale at Squadhelp.com!) (system is for sale at Squadhelp.com!) .Mail.RecipientCommand.Send(SmtpConnection conn, String to, String& response) at System.Net (system is for sale at Squadhelp.com!) (system is for sale at Squadhelp.com!) .Mail.SmtpTransport.SendMail(MailAddress sender, MailAddressCollection recipients, String deliveryNotify, Boolean allowUnicode, SmtpFailedRecipientException& exception) at System.Net (system is for sale at Squadhelp.com!) (system is for sale at Squadhelp.com!) .Mail.SmtpClient.Send(MailMessage message) at Nintex.Workflow.HumanApproval.Message.SendMessage(SmtpClient client, MailMessage msg) (Build:3520)
c713649f-b9b4-f0a3-29ad-fea8f512dc5f

 

Resolution

The error is being returned by the "Mimecast" mail filtering system:

Please see the following KB article

- https://community.mimecast.com/docs/DOC-1369#451

Or contact "Mimecast" support for further assistance.

Labels: (2)
Version history
Revision #:
5 of 5
Last update:
‎07-30-2020 09:00 AM
Updated by: