Unable to send attachment using Send-MailMessage - powershell

Question

Unable to send attachments using the Send-MailMessage cmdlet. The email sends with the subject and body, but no attachment.
Get-ADComputer -Filter {operatingsystem -like '*server*'} |
where {
$_.distinguishedname -notlike '*production*' -and
$_.distinguishedname -notlike '*tbd*' -and
$_.distinguishedname -notlike '*disabled*' -and
$_.distinguishedname -notlike '*domain controll*'
} |
Select Name, Distinguishedname |
Export-Csv -Path C:\Users\User1\wrongOU.csv |
Send-MailMessage -From 'from.email#gmail.com' -To 'to.email#gmail.com' -Subject 'This is a test email.' -SmtpServer smtp.test.com -Attachments "C:\Users\User1\File.txt" -Body 'This is a test email.'

Answer 1

The only parameter that accepts pipeline by value input is Attachments. If you perform a parameterbinding trace, you can see C:\Users\User1\File.txt bind to Attachments. Then the pipeline input is evaluated and a bind attempt is made. The attempt fails because there are no unbound parameters available to accept the value. When you bind that parameter in your command while piping an object into Send-MailMessage, PowerShell effectively removes the previously bound value (C:\Users\User1\File.txt) from binding to the Attachments parameter.
For successful command execution, you can do either of the following:
# For emailing File.txt
Send-MailMessage -From 'from.email#gmail.com' -To 'to.email#gmail.com' -Subject 'This is a test email.' -SmtpServer smtp.test.com -Attachments "C:\Users\User1\File.txt" -Body 'This is a test email.'
# For emailing wrongOU.csv
"C:\Users\User1\wrongOU.csv" | Send-MailMessage -From 'from.email#gmail.com' -To 'to.email#gmail.com' -Subject 'This is a test email.' -SmtpServer smtp.test.com -Body 'This is a test email.'
In short, the symptom is due to the parameter binding conflict that you have created. If you chose to leave off the -Attachments parameter with all else remaining the same, you would then have encountered issues because you are not piping a file path into the Send-MailMessage.
This exception and binding behavior appears to be typical for many built-in commands. A custom function does not exhibit these symptoms unless additional parameter validation is added. I would like to have more evidence as to what strips off the parameter value, but that remains to be seen.