MailKit/MimeKit giving error when on PowerShell 4 but works on PowerShell 5.1 - powershell-4.0

Question

I am getting the error, "Argument types do not match" when trying to send email using MailKit/MimeKit versions 2.5.1 when I am on the production server which is using PowerShell 4.0 but works on the developer machine using PowerShell 5.1
The system information for production and developer machines follow:
I get the error on production in the try/catch after it tries to run $MkSmtp.Send($Message):
The code I have looks as follows:
#Load the .NET Core class dll for Mailkit based on .NET 4.5
add-type -path "c:\Windows\System32\WindowsPowerShell\v1.0\Modules\EmailUtilities\MailKit.dll"
add-type -path "c:\Windows\System32\WindowsPowerShell\v1.0\Modules\EmailUtilities\MimeKit.dll"
#Server and Mailbox properties for less secure access when connecting to google
$MkSmtp = New-Object MailKit.Net.smtp.SmtpClient
$CanToken = New-Object System.Threading.CancellationToken ($false)
$SSL = [MailKit.Security.SecureSocketOptions]::SslOnConnect
$MkSmtp.Connect($MailServer, $Port, $SSL, $CanToken)
$MkSmtp.Authenticate(([System.Text.Encoding]::UTF8), $Username, $Password, $CanToken)
#have the building of the message in a separate function which also worked
#on development PowerShell 5.1 but not on production PowerShell 4 but rebuilt message
#here until I figure it out
#--------------
$Message = New-Object MimeKit.MimeMessage
$Message.From.Add($global:EmailFrom)
$Message.To.Add($global:EmailTo)
$Message.Subject = "Test";
$TextPart = New-Object MimeKit.TextPart ("plain")
$TextPart.Text = "Testing message..."
$Message.Body = $TextPart
#$Options = New-Object MimeKit.Net.Smtp.FormatOptions.Default.Clone
#$Options.International = $true
#$Message = New-MimeMessage $global:EmailFrom $global:EmailTo $Subject $LogMsg
$MkSmtp.Send($Message)
$MkSmtp.Disconnect($true)
$MkSmtp.Dispose()
#--------------

Answer 1

Updated our live server to Windows Management Framework 5.1 (PowerShell) and now works as expected just like my development machine.