Send-MailMessage : Mailbox unavailable. The server response was: 5.7.1 Unable to relay

You may receive the below error message when you try to execute PowerShell script to trigger email

 

 Send-MailMessage : Mailbox unavailable. The server response was: 5.7.1 Unable to relay
At C:\Temp\Get-ExchangeEnvironmentReport.ps1:1096 char:2
+     Send-MailMessage -Attachments $HTMLReport -To $MailTo -From $MailFrom -Subject ..

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   + CategoryInfo         : InvalidOperation: (System.Net.Mail.SmtpClient:SmtpClient) [Send-MailMessage], SmtpFailed   RecipientException
   + FullyQualifiedErrorId : SmtpException,Microsoft.PowerShell.Commands.SendMailMessage

To fix it out follow the below solution

Right click on McAfee icon



Click on Virus Scan Console



Double click on Access Protection on VirusScan Console - On Access Protection tab



Go to Anti-Virus Standard Protection - On right hand side, double click on Prevent mass mailing
worms from sending mail



On process to exclude tab, add PowerShell.exe at the end



Click ok