Move file to new folder if it does not exist already

Question

I have tried what feels like a million ways to do this and none of them are working like I want.
A file will be placed in folder 1 with a unique case number as the file name. IE 12345675.txt
If the data in the file is changed a new file with the same file name will be placed out again that contains the updated info (for now I don't care about the update.)
I want powershell to look for all the .txt files in folder 1 and compare them to the .txt files in folder 2 to see if that file name already exist.
If it does not exist, I want to send a email with the content of the file and then move the file from folder 1 to folder 2.
If it does exist then only move the file to folder 2 and overwrite the file that is already there.
Sample:
$folder1="C:\inetpub\cgi-bin" # Where Application will place incident file
$folder2="C:\incidents"       # Once file is processed it is moved here
$folder1Files=dir $folder1\*.txt    # Find all txt files in folder1
$folder2Files=dir $folder2\*.txt    # Find all txt files in folder2
$files = Get-ChildItem $folder1\*.txt   # Get all file that end with .txt
foreach ($file in $files){
    $testfile="$folder2\$file"    #I know there is something wrong here but can think of how to fix.
    if (!(Test-Path $testfile)){
                                Write-Host "NEW - Sending Page"
                                $to = "email address 1"
                                $from = "email address 2"
                                $subject = "Pre Alert"
                                $body = Get-Content -Path C:\inetpub\cgi-bin\*.txt
                                $smtpServer = "mail.domain2.com"
                                $smtpClient = New-Object Net.Mail.SmtpClient($smtpServer, 587)
                                $smtpClient.EnableSsl = $false
                                $smtpClient.Credentials = New-Object System.Net.NetworkCredential("Username",
"Password")
                                $smtpClient.Send($from, $to, $subject, $body)
                                Write-Host "Moving File"        
                                Move-Item -Path 'C:\inetpub\cgi-bin\$file' -Destination 'C:\incidents'
-verbose
                        else{
                                Remove-Item $file -include "*.txt"

Answer 1

$testfile="$folder2\$file"
What you're asking PowerShell to do there is to make a string which will start with the value of $folder2 (which you set earlier as a string) and then the value of $file, which is a document on the file system.
PowerShell is pretty good at changing a value from one form to another (in technical terms, 'casting') but it's always best to help it along where possible.
Why don't you try adding a 'Write-Host' line to say which file you're processing, and another line to say what file you're checking for. That should show you if you're building that string correctly or if you need to modify it.
For now comment out the email section and just try to get it to tell you if the file already exists or not. Once you've got that done then try to build out the email bit. The trick is always to build small steps in Scripts and only move on once you've tested
a section.
$folder1="C:\inetpub\cgi-bin" # Where Application will place incident file
$folder2="C:\incidents" # Once file is processed it is moved here
$folder1Files=dir $folder1\*.txt # Find all txt files in folder1
$folder2Files=dir $folder2\*.txt # Find all txt files in folder2
$files = Get-ChildItem $folder1\*.txt # Get all file that end with .txt
foreach ($file in $files){
$testfile="$folder2\$file" #I know there is something wrong here but can think of how to fix.
Write-Host "Checking for file at $testFile"
if (!(Test-Path $testfile)){
#Slightly modified
Write-Host "NEW - Sending Page " $file.Name
# $to = "email address 1"
# $from = "email address 2"
# $subject = "Pre Alert"
# $body = Get-Content -Path C:\inetpub\cgi-bin\*.txt
# $smtpServer = "mail.domain2.com"
# $smtpClient = New-Object Net.Mail.SmtpClient($smtpServer, 587)
# $smtpClient.EnableSsl = $false
# $smtpClient.Credentials = New-Object System.Net.NetworkCredential("Username", "Password")
# $smtpClient.Send($from, $to, $subject, $body)
Write-Host "Moving File"
Move-Item -Path 'C:\inetpub\cgi-bin\$file' -Destination 'C:\incidents' -verbose
else{ Write-Host "File found, skipping and deleting new file"
Remove-Item $file -include "*.txt"