Powershell send-MailMessage Exception

My script for sending emails using Office365 with an admin credentials. The script worked about 6 month, ago but recently it has not been working although it has not been changed.

I have tried to remove UseSsl but it did not work.

try {

    Send-MailMessage -To "myemail@domain.com" -Subject "test" `
        -From "support@domain.com" `
        -SmtpServer 'smtp.office365.com' -Port 587 -UseSsl:$true `
        -Credential $Cred -Body "testbody"
    Write-Host "Message sent to me." -BackgroundColor Black -ForegroundColor Green
}
catch [System.Exception] {
    throw $_
} 

Here is the exception I get:

Send-MailMessage : Transaction failed. The server response was: 5.2.0 STOREDRV.Submission.Exception:SendAsDeniedException.MapiExceptionSendAsDenied; Failed to process message due to a permanent exception with message Cannot submit message.