Powershell to Validate Email addresses - powershell

Question

I'm trying to get Powershell to validate email addresses using Regex and put email addresses into good and bad csv files. I can get it to skip one line and write to file, but cannot get it to target the email addresses and validate them, then write lines to good and bad files. I can do it in C# and JavaScript, but have never done it in Powershell. I know this can be done, but not sure how.
Here is what I have so far:
Function IsValidEmail {
Param ([string] $In)
# Returns true if In is in valid e-mail format.
[system.Text.RegularExpressions.Regex]::IsMatch($In,
"^([\w-\.]+)#((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.)|
(([\w-]+\.)+))([a-zA-Z]{2,4}|[0-9]{1,3})(\]?)$");
}
## Now we need to check the original file for invalid and valid emails.**
$list = Get-Content C:\Emails\OriginalEmails\emailAddresses.csv
# This way we also use the foreach loop.
##======= Test to see if the file exists ===========
if (!(Test-Path "C:\Emails\ValidEmails\ValidEmails.csv")) {
New-Item -path C:\Emails\ValidEmails -name ValidEmails.csv -type
"file" # -value "my new text"
Write-Host "Created new file and text content added"
}
else {
## Add-Content -path C:\Share\sample.txt -value "new text content"
Write-Host "File already exists and new text content added"
}
if (!(Test-Path "C:\Emails\InValidEmails\InValidEmails.csv")) {
New-Item -path C:\Emails\InValidEmails -name InValidEmails.csv -type
"file" # -value "my new text"
Write-Host "Created new file and text content added"
}
else {
# Add-Content -path C:\Emails\ValidEmails -value "new text content"
Write-Host "File already exists and new text content added"
}
#$Addresses = Import-Csv "C:\Data\Addresses.csv" -Header
Name, Address, PhoneNumber | Select -Skip 1
$EmailAddressImp = Import-Csv
"C:\Emails\OriginalEmails\emailAddresses.csv" -Header
FirstName, LastName, Email, Address, City, State, ZipCode | Select
FirstName, LastName, Email, Address, City, State, ZipCode -Skip 1
I'm validating the third column "Email" in the original csv file and trying to write out the whole row to file (good file, bad file). Not sure how to buffer either doing this.
ForEach ($emailAddress in $list) {
if (IsValidEmail($emailAddress)) {
"Valid: {0}" -f $emailAddress
Out-File -Append C:\Emails\ValidEmails\ValidEmails.csv -Encoding UTF8
$EmailAddressImp | Export-Csv "C:\Emails\ValidEmails\ValidEmails.csv"
-NoTypeInformation
}
else {
"Invalid: {0}" -f $emailAddress
Out-File -Append C:\Emails\InValidEmails\InValidEmails.csv -
Encoding UTF8
$EmailAddressImp | Export-Csv
"C:\Emails\InValidEmails\InValidEmails.csv" -NoTypeInformation
}
}

Answer 1

I'm trying to get Powershell to validate email addresses using Regex
Don't!
I would recommend against this. Accurately validating email addresses using regular expressions can be much more difficult than you might think.
Let's have a look at your regex pattern:
^([\w-\.]+)#((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.)|(([\w-]+\.)+))([a-zA-Z]{2,4}|[0-9]{1,3})(\]?)$
In it's current form it incorrectly validates .#domain.tld.
On the other hand, it doesn't validate unicode-encoded internationalized domain names, like user#☎.com (yes, that's a valid email address)
Instead of trying to find or construct a perfect email validation regex pattern, I would use the MailAddress class for validation instead:
function IsValidEmail {
param([string]$EmailAddress)
try {
$null = [mailaddress]$EmailAddress
return $true
}
catch {
return $false
}
}
If the input string is a valid email address, the cast to [mailaddress] will succeed and the function return $true - if not, the cast will result in an exception, and it returns $false.
When exporting the data, I'd consider collecting all the results at once in memory and then writing it to file once, at the end.
If you're using PowerShell version 2 or 3, you can do the same with two passes of Where-Object:
$EmailAddresses = Import-Csv "C:\Emails\OriginalEmails\emailAddresses.csv" -Header FirstName, LastName, Email, Address, City, State, ZipCode | Select -Skip 1
$valid = $list |Where-Object {IsValidEmail $_.Email}
$invalid = $list |Where-Object {-not(IsValidEmail $_.Email)}
If you're using PowerShell version 4.0 or newer, I'd suggest using the .Where() extension method in Split mode:
$EmailAddresses = Import-Csv "C:\Emails\OriginalEmails\emailAddresses.csv" -Header FirstName, LastName, Email, Address, City, State, ZipCode | Select -Skip 1
$valid,$invalid = $list.Where({IsValidEmail $_.Email}, 'Split')
before exporting to file:
if($valid.Count -gt 0){
$valid |Export-Csv "C:\Emails\ValidEmails\ValidEmails.csv" -NoTypeInformation
}
if($invalid.Count -gt 0){
$invalid |Export-Csv "C:\Emails\ValidEmails\InvalidEmails.csv" -NoTypeInformation
}

Answer 2

You can just use the -match operator, instead of calling into the [Regex] class. Here's a simple example, without any wrapper function:
$EmailRegex = '^([\w-\.]+)#((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.)|(([\w-]+\.)+))([a-zA-Z]{2,4}|[0-9]{1,3})(\]?)$'
$EmailList = #('a#a.com', 'b#b.co', 'm.a#example.il')
foreach ($Email in $EmailList) {
$DidItMatch = $Email -match $EmailRegex
if ($DidItMatch) {
# It matched! Do something.
}
else {
# It didn't match
}
}
FYI, when you use the -match operator, if it returns boolean $true, then PowerShell automatically populates a built-in (aka. "automatic") variable called $matches. To avoid unexpected behavior, you might want to reset this variable to $null during each iteration, or just wrap it in a function as you did in your original example. This will keep the variable scoped to the function level, as long as you don't declare it in one of the parent scopes.
Once you've validated the e-mail address, you can append it to your existing CSV file, using:
Export-Csv -Append -FilePath filepath.csv -InputObject $Email
For efficiency with the available filesystem resources, you'll probably want to buffer a few e-mail addresses in memory, before appending them to your target CSV file.
# Initialize a couple array buffers
$ValidEmails = #()
$InvalidEmails = #()
if ($ValidEmails.Count -gt 50) {
# Run the CSV export here
}
if ($Invalid.Count -gt $50) {
# Run the CSV export here
}
If you need further help, can you please edit your question and clarify what isn't working for you?

Answer 3

Each of the current top 2 answers here has one significant deficiency:
#Trevor's answer would do just fine, until you supply it this:
John Doe <johndoe#somewhere.com>
#Mathias' answer preaches about accommodating exceptional (yet valid) addresses such as those with non-ASCII or no TLD suffix. The following addresses all validate successfully with the [mailaddress] casting:
olly#somewhere | olly#somewhere. | olly#somewhere...com etc
If, like me, you will not be entertaining these edge cases into your email databases, then a combination of both ideas might prove more useful, like so:
function IsValidEmail {
param([string]$Email)
$Regex = '^([\w-\.]+)#((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.)|(([\w-]+\.)+))([a-zA-Z]{2,4}|[0-9]{1,3})(\]?)$'
try {
$obj = [mailaddress]$Email
if($obj.Address -match $Regex){
return $True
}
return $False
}
catch {
return $False
}
}
Perhaps there is a performance overhead with creating $obj for every email address on a possibly long mailing list. But I guess that's another matter.

Answer 4

You can use the mailaddress type to ensure it meets RFC, but you will likely still want to make sure the domain is valid:
Resolve-DnsName -Name ('vertigoray#example.com' -as [mailaddress]).Host -Type 'MX'
Works well as a validation script for a function parameter:
function Assert-FromEmail {
param(
[Parameter(Mandatory = $true)]
[ValidateScript({ Resolve-DnsName -Name $_.Host -Type 'MX' })]
[mailaddress]
$From
)
Write-Output $From
}
Output examples of that function on success:
PS > Assert-FromEmail -From vertigoray#example.com
DisplayName User Host Address
----------- ---- ---- -------
vertigoray example.com vertigoray#example.com
Output examples of that function on failure:
PS > Assert-FromEmail -From vertigoray#example..com
Assert-FromEmail : Cannot validate argument on parameter 'From'. The " Resolve-DnsName -Name $_.Host -Type 'MX' "validation script for the argument with value "vertigoray#example..com" did not return a result of True. Determine why the validation script failed, and then try the command again.
At line:1 char:24
+ Assert-FromEmail -From vertigoray#example..com
+ ~~~~~~~~~~~~~~~~~~~~~~~
+ CategoryInfo : InvalidData: (:) [Assert-FromEmail], ParameterBindingValidationException
+ FullyQualifiedErrorId : ParameterArgumentValidationError,Assert-FromEmail

Answer 5

Here is one to try I wrote up and tested and has not failed me in any environment to date. Not, saying it won't in someone else's, but for me, it's been 100%.
$SomeEmailAddresses = #'
From:JoeBob#yahoo.com,Tom TheCat tcat#snailmail.net,jerry#snailmail.net
To:TulaJane#hotmail.com;JF#gmail.com;tiger#outlook.com;
Doug Tompson DTompson#icloud.com
MailTo:BobsYourUncle#protonmail.com;
johnny.bravo#yahoo.co.uk
'#
(((Select-String -InputObject $SomeEmailAddresses `
-Pattern '\w+#\w+\.\w+|\w+\.\w+#\w+\.\w+\.\w+' `
-AllMatches).Matches).Value)
Rsults
JoeBob#yahoo.com
tcat#snailmail.net
jerry#snailmail.net
TulaJane#hotmail.com
JF#gmail.com
tiger#outlook.com
DTompson#icloud.com
BobsYourUncle#protonmail.com
johnny.bravo#yahoo.co.uk

Answer 6

#postanote
This common email formatting fails
$SomeEmailAddresses = #'
First A. Last first.a.last#gmail.com.
'#
(((Select-String -InputObject $SomeEmailAddresses -Pattern '\w+#\w+\.\w+|\w+\.\w+#\w+\.\w+\.\w+'
-AllMatches).Matches).Value)

Answer 7

Here is the code I use.
The regex does not support the following because the major email players do not support.
Domains as IP addresses.
Space and special characters "(),:;<>#[] inside a quoted string in local-part.
Comments within parentheses in local-part.
$email = "^(?(?=^(?:([a-zA-Z0-9_!#$%&'+-/=?^{|}~]+|[a-zA-Z0-9_!#$%&'*+\-\/=?^{|}~].[a-zA-Z0-9_!#$%&'+-/=?^{|}~][\.a-zA-Z0-9_!#$%&'*+\-\/=?^{|}~]))#[a-zA-Z0-9.-]{1,63}$)[a-zA-Z0-9_.!#$%&'*+-/=?^`{|}~]{1,63}#[a-zA-Z0-9-]+(?:.[a-zA-Z0-9-]{2,})+)$"
$email -match $regexPattern