Here is my powershell to send an email from my smtp server. 

My real smtp server exists and functions correctly.

This PS script takes a long time to run and below is the error code:

$subject = "This Subject"
$body =  "The Body and the subBody"
$emailTo = "toemail@email.com"
$emailFrom ="fromemail@email.com"
$smtpServer = smtp.email.com
$port="25"
$smtp = new-object Net.Mail.SmtpClient($smtpServer)
$credentials=new-object system.net.networkcredential(email@email.com,password)
$smtp.credentials=$credentials.getcredential($smtpserver,$port)
$PlainPassword = "mainpassword"
$SecurePassword = $PlainPassword | ConvertTo-SecureString -AsPlainText -Force 
$UserName = "MYSITE\Administrator"
$Credentials = New-Object System.Management.Automation.PSCredential -ArgumentList $UserName, $SecurePassword 
Send-MailMessage -To $emailTo -Subject $subject -Body $body -SmtpServer $smtpServer -From $emailFrom -Credential $Credentials -Port $port -UseSsl

PS Error Code:

InvalidOperation: (System.Net.Mail.SmtpClient:SmtpClient) [Send-MailMessage], SmtpException

• Edited by Philosophiae 7 hours 19 minutes ago

If your smtp server allows email to be relayed then this is easier:

$mailprops=@{
    Subject = 'This Subject'
    Body = 'The Body and the subBody'
    To = 'toemail@email.com'
    From = 'fromemail@email.com'
    SmtpServer = 'smtp.email.com'
}
Send-MailMessage @mailprops -Credential mailuserid

You must avoid smart quotes which you mayl get when copying form a web page.

I an still getting an error on the SmtpServer even with the smtp credentials

$PlainPassword = 'pass1'
$SecurePassword = $PlainPassword | ConvertTo-SecureString -AsPlainText -Force 
$UserName = email1@email.com'
$smtpcredentials = New-Object System.Management.Automation.PSCredential -ArgumentList $UserName, $SecurePassword 
$subject = 'This Subject'
$body =  'The Body and the rest of the Body'
$emailTo = 'emailto@email.com
$emailFrom ='emailfrom@email.com'
$smtpServer = 'smtp.email.com'
$port='25'
Send-MailMessage -To $emailTo -Subject $subject -Body $body -SmtpServer $smtpServer -From $emailFrom -Credential $smtpcredentials -Port $port -UseSsl

I get Send-MailMessage  from here:

https://technet.microsoft.com/en-us/library/hh849925.aspx?f=255&MSPPError=-2147217396

• Edited by Philosophiae 4 hours 0 minutes ago

The instructions are specific. The Credentials take a PsCredential object and not what you are passing. Do it my way until you understand how to make it work then you can try and change it how you like..