Try changing this code :
$smtpClient = New-Object System.Net.Mail.SmtpClient
$mailMessage = New-Object System.Net.Mail.MailMessage
$smtpClient.host = $SmtpHost
$mailMessage.To.add($To)
$mailMessage.from = $From
$mailMessage.Subject = $Subject
$mailMessage.Body = "Email from WFA system:`n"
$smtpClient.Port = 25
Get-WFALogger -Info -message $("Sending email to " + $To)
$smtpClient.Send($mailMessage)