Matching content between 2 CSVs and write the values - powershell

Question

Each user has a domain1.com and domain2.com separate email address. I would like to compare email addresses within CSV1 & CSV2 and if the prefix name on their emails match, pull the value into CSV1. This will later allow me to run other powershell commands on a source / target kind of scenario.
I have it somewhat, working below although the domain2_email column isn't matching the user row. It looks to be trying to import all of them into an array.
I have used Joe.Bloggs here to test if the IF is working, but ideally - I would like to have it search each entry in CSV1.
End Goal:
Search CSV2 with the name part of the primarySMTPAddress value and if match, put them into another column within CSV1.
CSV1 will have a user with domain1.com and domain2.com values within the row.
# Pull in mailbox data
Get-EXOMailbox -Filter {EmailAddresses -like *#domain1.com -and RecipientTypeDetails -notlike "SharedMailbox"} | Export-Csv -Path './domain1export.csv'
Get-EXOMailbox -Filter {EmailAddresses -like *#domain2.com -and RecipientTypeDetails -notlike "SharedMailbox"} | Export-Csv -Path './domain2xexport.csv'
$outfile = './outfile.csv'
$finalOutfile = './finalOutfile.csv'
# Check if outfile.csv exists, if it does - delete.
if (test-path $outfile) {
Remove-Item $outfile
Write-Host "$outfile has been deleted"
}
$CSV1 = Import-Csv -Path './domain1export.csv'
$CSV2 = Import-Csv -Path './domain2export.csv'
$CVS1 | foreach {
# Splits the name prefix from email
$_ | Select-Object *,#{Name='Name_Prefix';Expression={$_.PrimarySmtpAddress.Split("#")[0] }} | Export-Csv -Path $outfile -Append -NoTypeInformation
}
$outfile2 = Import-Csv -Path $outfile
foreach ($item in $outfile2) {
if ($outfile2.Name_Prefix -match "Joe.Bloggs") {
$item | Select-Object *,#{Name='Domain2_email';Expression={$CSV2.PrimarySmtpAddress}} | Export-Csv -Path $finalOutfile -Append -NoTypeInformation
}
}
Data
CSV1
UserPrincipalName,Alias,DisplayName,EmailAddresses,PrimarySmtpAddress,RecipientType,RecipientTypeDetails
joe.bloggs#domain1.com,d1bloggsj,Domain1 Joe Bloggs,SIP:joe.blogggs#domain1.com SMTP:joe.blogggs#domain1.com,Joe.Bloggs#domain1.com,UserMailbox,UserMailbox
foo.bar#domain1.com,d1barf,Domain1 Foo Bar,SIP:foo.bar#domain1.com SMTP:foo.bar#domain1.com ,foo.bar#domain1.com,UserMailbox,UserMailbox
CSV2
UserPrincipalName,Alias,DisplayName,EmailAddresses,PrimarySmtpAddress,RecipientType,RecipientTypeDetails
joe.bloggs#domain2.com,d2bloggsj,Domain2 Joe Bloggs,SIP:joe.blogggs#domain2.com SMTP:joe.blogggs#domain2.com,Joe.Bloggs#domain2.com,UserMailbox,UserMailbox
foo.bar#domain2.com,d1barf,Domain2 Foo Bar,SIP:foo.bar#domain2.com SMTP:foo.bar#domain2.com ,foo.bar#domain2.com,UserMailbox,UserMailbox

Answer 1

So both CSV1 and CSV2 would contain a column called PrimarySmtpAddress and you need to match those, correct?
Try
$CSV1 = Import-Csv -Path './domain1export.csv'
$CSV2 = Import-Csv -Path './domain2export.csv'
$result = foreach ($item in $csv1) {
$prefix = $item.PrimarySmtpAddress.Split("#")[0]
# try and find a match
$matching = $csv2 | Where-Object { $_.PrimarySmtpAddress.Split("#")[0] -eq $prefix }
$item | Select-Object *, #{Name = 'Name_Prefix'; Expression = {$prefix }},
#{Name = 'Domain2_email';Expression = {$matching.PrimarySmtpAddress }}
}
$finalOutfile = './finalOutfile.csv'
$result | Export-Csv -Path $finalOutfile -NoTypeInformation
BTW. According to the docs, the -Filter parameter is a string, not a scriptblock, so you should use
Get-EXOMailbox -Filter "EmailAddresses -like '*#domain1.com' -and RecipientTypeDetails -ne 'SharedMailbox'"

Answer 2

I would do it like this, first create a hash table using the Csv1 where the Keys are the mail prefix and the Values are the mail suffix and the, using a calculated property with Select-Object you can search for each line on Csv2 if the mail's prefix exists and obtain the corresponding Values (mail suffix):
Note, below code assumes that there are unique mail prefixes, if this was not the case, an if condition would need to be added to the first loop to avoid Key collision. I would also recommend you to use the MailAddress Class to parse your emails.
$map = #{}
foreach($line in $csv1) {
$mail = [mailaddress]$line.PrimarySmtpAddress
$map[$mail.User] = $mail
}
$csv2 | Select-Object *, #{
Name = 'SecondaryDomain'
Expression = { $map[([mailaddress]$_.PrimarySmtpAddress).User].Host }
}, #{
Name = 'SecondarySmtpAddress'
Expression = { $map[([mailaddress]$_.PrimarySmtpAddress).User].Address }
}
$result | Format-Table