PowerShell runs on Windows 8.1 PS v4.0, but fails on 2008R2 PS v2.0

Question

I developed a PS script to run on my server to discover if certain files exist*. I developed the code on Win 8.1 64-bit which has PS version 4.0 installed. It works perfectly. I copied the files to my Win 2008R2 SP1 64-bit server with PS version 2.0 (script
is called from a .bat file which just loads the script and allows it run).
Both computers use Comcast as the ISP, but are in different locations. The code fails on the server with an Invalid HELO name from the mail server coming from the very last line of code below. This mail server does require SMTP_AUTH, but as noted above it
works just fine from the Win 8 machine.
I believe the code is all PS v2.0, but could be wrong about that.
*I replaced the lookup logic for testing so my configuration is irrelevant (code shown just gets today's date instead of looking up specific data).
Any suggestions for a fix?
$todaysDate = (Get-Date -UFormat "%m-%d-%Y")
#irrelevant code removed/modified
$content = $todaysDate
$emailFrom = "[email protected]"
$emailTo = "[email protected], [email protected]"
$subject = "Batch Files for " + $todaysDate
$body = "Found the following Batch files dated: " + $todaysDate + "`n" + $content
$smtpServer = "smtp.mydomain.com"
$mypass = "password"
# use a SecureString for $mypass which you can save to disk via Export-Clixml or ConvertFrom-SecureString
$SMTPMessage = New-Object System.Net.Mail.MailMessage($EmailFrom,$EmailTo,$Subject,$Body)
$SMTPClient = New-Object Net.Mail.SmtpClient($SmtpServer, 587)
$SMTPClient.EnableSsl = $false
$SMTPClient.Credentials = New-Object System.Net.NetworkCredential($emailFrom, $mypass)
$SMTPClient.Send($SMTPMessage)
The failure error msg (line 22 is the last line of code with lookup logic in place):
C:\rmwin\BATCHES>REM marks comments
C:\rmwin\BATCHES>REM NO ECHO
C:\rmwin\BATCHES>cd c:\rmwin\BATCHES\
C:\rmwin\BATCHES>PowerShell.exe -NoProfile -ExecutionPolicy Bypass -Command "& '
C:\rmwin\BATCHES\BatchesSent.ps1'"
Exception calling "Send" with "1" argument(s): "Mailbox unavailable. The server
 response was: Access denied - Invalid HELO name (See RFC2821 4.1.1.1)"
At C:\rmwin\BATCHES\BatchesSent.ps1:22 char:17
+ $SMTPClient.Send <<<< ($SMTPMessage)
+ CategoryInfo         
: NotSpecified: (:) [], MethodInvocationException
+ FullyQualifiedErrorId : DotNetMethodException

Answer 1

You are authenticating:
$SMTPClient = New-Object
Net.Mail.SmtpClient($SmtpServer,
587)
$SMTPClient.EnableSsl = $false
$SMTPClient.Credentials =
New-Object
System.Net.NetworkCredential($emailFrom,$mypass)
$SMTPClient.Send($SMTPMessage)
I suspect you have other issues.
¯\_(ツ)_/¯