This works:

$emailSmtpServer = "box300.bluehost.com"
$emailSmtpServerPort = "26"

$emailSmtpUser = "george@skydivingphotography.com"
$emailSmtpPass = "******" #ommited for security

$emailMessage = New-Object System.Net.Mail.MailMessage
$emailMessage.From = "george@skydivingphotography.com"
$emailMessage.To.Add("george_katsoulis@yahoo.co.uk")
$emailMessage.Subject = "subject"
$emailMessage.Body = "body"

$SMTPClient = New-Object System.Net.Mail.SmtpClient($emailSmtpServer, $emailSmtpServerPort)
$SMTPClient.Credentials = New-Object System.Net.NetworkCredential($emailSmtpUser, $emailSmtpPass);
$SMTPClient.Send($emailMessage)


This does not:

$emailSmtpServer = "box300.bluehost.com"
$emailSmtpServerPort = "465"

$emailSmtpUser = "george@skydivingphotography.com"
$emailSmtpPass = "******" #ommited for security

$emailMessage = New-Object System.Net.Mail.MailMessage
$emailMessage.From = "george@skydivingphotography.com"
$emailMessage.To.Add("george_katsoulis@yahoo.co.uk")
$emailMessage.Subject = "subject"
$emailMessage.Body = "body"

$SMTPClient = New-Object System.Net.Mail.SmtpClient($emailSmtpServer, $emailSmtpServerPort)
$SMTPClient.Credentials = New-Object System.Net.NetworkCredential($emailSmtpUser, $emailSmtpPass);
$SMTPClient.EnableSsl = $true
$SMTPClient.Send($emailMessage)