tommymaynard/technet-check_email_address_domain_against.ps1

## technet-check_email_address_domain_against.ps1
<#
TechNet Contribution: Check Email Address Domain Against the Top-Level Domain List from IANA
Previous link: https://gallery.technet.microsoft.com/Check-Email-Address-Domain-41cb7838
Downloaded: 496 times (as of 05/21/2020)

At times it seems that there has been some frustration when trying to validate an email address. In my experience,
this often been because an email address without a domain (.com, .net, .org) is often validated as True. While the
purpose of this advanced function is not to validate an entire email address, it does validate the domain according
to the Internet Assigned Numbers Authority (IANA).

This advanced function will download a top-level domain (TLD) list from IANA, store it in a file, and then compare
he domain of an email address, or a given string, against the TLD file. It has other features that will allow it work
from an existing TLD file, if the file has already been downloaded in the last day, or if there is no Internet
connection. By default, it will only return True or False, but using the -MoreInfo and -ShowVars parameters will return
more information. In addition, there is a -Days parameter that can be useful as well. Using this parameter will force
updating the TLD file (-Days -1) or force the function to use the TLD file, providing it already has one, even if it is
over a day old (-Days 20, -Days 100, etc.).

Finally, this advanced function only works with Windows PowerShell 3.0 and greater

Please report any problems that you may find so they can be corrected.

Tommy Maynard

http://tommymaynard.com
#>

Function Find-TMEmailTLD {
##### ** THIS SCRIPT IS PROVIDED WITHOUT WARRANTY, USE AT YOUR OWN RISK **

<#
.SYNOPSIS
    Determines if a string is on the top-level domain (TLD) list from Internet Assigned Numbers Authority (IANA) (https://www.iana.org/).

.DESCRIPTION
    The Find-TMEmailTLD advanced function accepts a string as input. If the string includes a dot character, such as expected in an email address, it will check the string after the final dot character. If it does not include a dot character it will simply check the provided string. It will ultimately compare the the string against the TLD file that is created by downloading a list of TLDs provided by IANA.

.PARAMETER String
    This is the default, required parameter. It is the string that the function will compare to the TLD file.

.PARAMETER Days
    By default the script will not update the TLD file, providing it has already has a TLD file, unless the file was last written over 1 day ago. This parameter allows the user to change the default value to as many or as few days as desired. Use a negative number to force the TLD file download or a very large number if the file has already been downloaded and a new one is not needed, or there is no Internet connection.

.PARAMETER MoreInfo
    By default the function will only return True or False. Using this parameter will include a small amount of additional information.

.PARAMETER ShowVars
    Using this parameter will tell the function to display the values stored in the variables used by this function. Although this is a carryover from development, it could be helpful in both understanding the function and troubleshooting any errors.

.EXAMPLE
    Find-TMEmailTLD -String user@domain.com
    This example will isolate com and check it against the TLD file from IANA. By default this function only returns True or False.

.EXAMPLE
    Find-TMEmailTLD mil -MoreInfo -ShowVars
    The example will check mil against the TLD file from IANA. In addition, it will display a few other pieces of information, including the values stored in the variables used in the script.

.EXAMPLE
    Find-TMEmailTLD xxy -Days 10
    This example will check xxy against the TLD file from IANA. In addition, it will only download a new version of the TLD file if the file already exists and is older than 10 days.

.NOTES
    NAME: Find-TMEmailTLD
    AUTHOR: Tommy Maynard
    LASTEDIT: 06/16/2014
    VERSION: 1.2
    NOTES: This is the first version (1.2) uploaded to the TechNet Gallery.
#>

    [CmdletBinding()]
    Param(
        [Parameter(Mandatory=$True,Position=0)]
        [string]$String,
        [Parameter(Position=1)]
        [int]$Days = 1,
        [switch]$MoreInfo,
        [switch]$ShowVars
    )

    Begin {
        ##### Test for Internet Connection ; requires ICMP/Ping to Internet
        Write-Verbose -Message 'Checking for Internet connection'
        If ((Test-Connection 'pingomatic.com' -Quiet -Count 1) -or (Test-Connection -ComputerName 'pinging.com' -Quiet -Count 1)) {
            Write-Verbose -Message 'Internet connecion available'
            $InternetConnection = $True
        } Else {
            $InternetConnection = $False
        }

        ##### Checking for TLD File ; Downloading if necessary
        Write-Verbose -Message 'Checking for TLD file from IANA'

        If ($PSVersionTable.PSVersion.Major -le 2) {
            Write-Warning -Message 'Run this function with the -MoreInfo parameter.'
            $WrongVersion = $True
            $OutputCode = 6
        } ElseIf ($PSVersionTable.PSVersion.Major -ge 3) {
            $FileLocation = "$PSScriptRoot\tlds.txt"
        }

        If ($WrongVersion -ne $True) {
            $FileLocation = "$PSScriptRoot\tlds.txt"
            If (Test-Path -Path $FileLocation) {
                Write-Verbose -Message 'TLD file from IANA found'
                $FileInfo = Get-ChildItem -File $FileLocation | select -ExpandProperty LastWriteTime
                $TimeSinceDownload = New-TimeSpan -Start $FileInfo -End (Get-Date) | Select-Object -ExpandProperty Days

                Write-Verbose -Message 'Checking TLD file age'
                If ($TimeSinceDownload -ge $Days -and $InternetConnection -eq $True) {
                    Write-Verbose -Message "TLD file needs to be replaced (Days: $Days)"
                    $GetNewFile = $True
                    $LoadExistingFile = $False
                }
                Else {
                    Write-Verbose -Message 'TLD file does not need to be replaced'
                    $LoadExistingFile = $True
                    $GetNewFile = $False
                }

            } ElseIf ($InternetConnection -eq $True) {
                Write-Verbose -Message 'TLD file needs to be replaced'
                $GetNewFile = $True
            } Else {
                $TLDList = $NULL
            }

            ##### Get New File or Load Existing TLD File
            If ($GetNewFile) {
                try {
                    Write-Verbose -Message 'Downloading TLD file'
                    $FileURL = 'http://data.iana.org/TLD/tlds-alpha-by-domain.txt'
                    $TLDList = (Invoke-WebRequest -Uri $FileURL).Content
                    Set-Content -Path $FileLocation -Value $TLDList
                    $TLDList = Get-Content -Path $FileLocation | Where-Object {$_ -notlike '#*' -and $_ -notlike ''}
                }
                catch {
                    $TLDList = $NULL
                    Write-Warning -Message 'Run this function with the -MoreInfo parameter.'
                }
            } ElseIf ($LoadExistingFile) {
                Write-Verbose -Message 'Loading existing TLD file'
                $TLDList = Get-Content -Path $FileLocation | Where-Object {$_ -notlike '#*' -and $_ -notlike ''}
            } Else {
                $TLDList = $NULL
            }
        }
    } # End Begin

    Process {
        ##### Check string against TLD list
        If ($WrongVersion -ne $True) {
            Write-Verbose -Message 'Checking that TLD file has entries/values'
            If ($TLDList -ne $NULL) {
            Write-Verbose -Message 'Checking string against TLD file'
            $String = ($String.Split('.')[-1]).Trim().ToLower()
                If (-not($String.Length -le 0)) {
                    If ($TLDList | Select-String "^$String$") {
                        Write-Output -Verbose $True
                        $OutputCode = 1
                    } ElseIf (-not($TLDList | Select-String "^$String$")) {
                        Write-Output -Verbose $False
                        $OutputCode = 2
                    }
                } Else {
                    $OutputCode = 3
                    Write-Output -Verbose $False
                }
            } ElseIf ($InternetConnection -eq $False -and $TLDList -eq $NULL) {
                $OutputCode = 4
            } ElseIf (($InternetConnection -eq $True -and $TLDList -eq $NULL) -or ($TLDList -eq $NULL)) {
                $OutputCode = 5
            } Else {
                $OutputCode = 7
            }
        }

        ##### Write output message (-MoreInfo parameter)
        If ($MoreInfo) {
            Write-Verbose -Message 'MoreInfo parameter specified'
            switch ($OutputCode) {
                1 {Write-Output -Verbose "SUCCESS: $String`r`nMESSAGE: This TLD matches the TLD file from IANA."}
                2 {Write-Output -Verbose "FAILURE: $String`r`nMESSAGE: This TLD does not match the TLD file from IANA."}
                3 {Write-Output -Verbose "ERROR: $String`r`nMESSAGE: A usable string has not been entered."}
                4 {Write-Output -Verbose "ERROR: $String`r`nMESSAGE: No Internet Connection and No TLD file."}
                5 {Write-Output -Verbose "ERROR: $String`r`nMESSAGE: IANA URL may have changed ($FileURL) or no access to write TLD file (Check UAC)."}
                6 {Write-Output -Verbose "ERROR: Version`r`nMESSAGE: This advanced function requires Windows PowerShell 3.0 or greater."}
                7 {Write-Output -Verbose "ERROR: $String`r`nMESSAGE: Unknown Error (Output Code: $OutputCode"}
                default {Write-Output -Verbose "ERROR: $String`r`nMESSAGE: Unknown error (Output Code: Default)."}
            }
        }

        ##### Display variables' values (-ShowVars parameter)
        If ($ShowVars) {
            Write-Verbose -Message 'ShowVars parameter specified'
            Write-Output "----- Variables -----"
                "String: $String",
                "Internet Connection: $InternetConnection",
                "File Location: $FileLocation",
                "File Last Write Time: $FileInfo",
                "Days Since Download: $TimeSinceDownload day(s)"
                "Days Specified: $Days day(s)",
                "Get New File: $GetNewFile",
                "Load Existing File: $LoadExistingFile",
                "Output Code: $OutputCode"
                "Show Variables: $ShowVars"
        }
    } # End Process
} # End Function
	<#
	TechNet Contribution: Check Email Address Domain Against the Top-Level Domain List from IANA
	Previous link: https://gallery.technet.microsoft.com/Check-Email-Address-Domain-41cb7838
	Downloaded: 496 times (as of 05/21/2020)

	At times it seems that there has been some frustration when trying to validate an email address. In my experience,
	this often been because an email address without a domain (.com, .net, .org) is often validated as True. While the
	purpose of this advanced function is not to validate an entire email address, it does validate the domain according
	to the Internet Assigned Numbers Authority (IANA).

	This advanced function will download a top-level domain (TLD) list from IANA, store it in a file, and then compare
	he domain of an email address, or a given string, against the TLD file. It has other features that will allow it work
	from an existing TLD file, if the file has already been downloaded in the last day, or if there is no Internet
	connection. By default, it will only return True or False, but using the -MoreInfo and -ShowVars parameters will return
	more information. In addition, there is a -Days parameter that can be useful as well. Using this parameter will force
	updating the TLD file (-Days -1) or force the function to use the TLD file, providing it already has one, even if it is
	over a day old (-Days 20, -Days 100, etc.).

	Finally, this advanced function only works with Windows PowerShell 3.0 and greater

	Please report any problems that you may find so they can be corrected.

	Tommy Maynard

	http://tommymaynard.com
	#>

	Function Find-TMEmailTLD {
	##### THIS SCRIPT IS PROVIDED WITHOUT WARRANTY, USE AT YOUR OWN RISK

	<#
	.SYNOPSIS
	Determines if a string is on the top-level domain (TLD) list from Internet Assigned Numbers Authority (IANA) (https://www.iana.org/).

	.DESCRIPTION
	The Find-TMEmailTLD advanced function accepts a string as input. If the string includes a dot character, such as expected in an email address, it will check the string after the final dot character. If it does not include a dot character it will simply check the provided string. It will ultimately compare the the string against the TLD file that is created by downloading a list of TLDs provided by IANA.

	.PARAMETER String
	This is the default, required parameter. It is the string that the function will compare to the TLD file.

	.PARAMETER Days
	By default the script will not update the TLD file, providing it has already has a TLD file, unless the file was last written over 1 day ago. This parameter allows the user to change the default value to as many or as few days as desired. Use a negative number to force the TLD file download or a very large number if the file has already been downloaded and a new one is not needed, or there is no Internet connection.

	.PARAMETER MoreInfo
	By default the function will only return True or False. Using this parameter will include a small amount of additional information.

	.PARAMETER ShowVars
	Using this parameter will tell the function to display the values stored in the variables used by this function. Although this is a carryover from development, it could be helpful in both understanding the function and troubleshooting any errors.

	.EXAMPLE
	Find-TMEmailTLD -String user@domain.com
	This example will isolate com and check it against the TLD file from IANA. By default this function only returns True or False.

	.EXAMPLE
	Find-TMEmailTLD mil -MoreInfo -ShowVars
	The example will check mil against the TLD file from IANA. In addition, it will display a few other pieces of information, including the values stored in the variables used in the script.

	.EXAMPLE
	Find-TMEmailTLD xxy -Days 10
	This example will check xxy against the TLD file from IANA. In addition, it will only download a new version of the TLD file if the file already exists and is older than 10 days.

	.NOTES
	NAME: Find-TMEmailTLD
	AUTHOR: Tommy Maynard
	LASTEDIT: 06/16/2014
	VERSION: 1.2
	NOTES: This is the first version (1.2) uploaded to the TechNet Gallery.
	#>

	[CmdletBinding()]
	Param(
	[Parameter(Mandatory=$True,Position=0)]
	[string]$String,
	[Parameter(Position=1)]
	[int]$Days = 1,
	[switch]$MoreInfo,
	[switch]$ShowVars
	)

	Begin {
	##### Test for Internet Connection ; requires ICMP/Ping to Internet
	Write-Verbose -Message 'Checking for Internet connection'
	If ((Test-Connection 'pingomatic.com' -Quiet -Count 1) -or (Test-Connection -ComputerName 'pinging.com' -Quiet -Count 1)) {
	Write-Verbose -Message 'Internet connecion available'
	$InternetConnection = $True
	} Else {
	$InternetConnection = $False
	}

	##### Checking for TLD File ; Downloading if necessary
	Write-Verbose -Message 'Checking for TLD file from IANA'

	If ($PSVersionTable.PSVersion.Major -le 2) {
	Write-Warning -Message 'Run this function with the -MoreInfo parameter.'
	$WrongVersion = $True
	$OutputCode = 6
	} ElseIf ($PSVersionTable.PSVersion.Major -ge 3) {
	$FileLocation = "$PSScriptRoot\tlds.txt"
	}

	If ($WrongVersion -ne $True) {
	$FileLocation = "$PSScriptRoot\tlds.txt"
	If (Test-Path -Path $FileLocation) {
	Write-Verbose -Message 'TLD file from IANA found'
	$FileInfo = Get-ChildItem -File $FileLocation \| select -ExpandProperty LastWriteTime
	$TimeSinceDownload = New-TimeSpan -Start $FileInfo -End (Get-Date) \| Select-Object -ExpandProperty Days

	Write-Verbose -Message 'Checking TLD file age'
	If ($TimeSinceDownload -ge $Days -and $InternetConnection -eq $True) {
	Write-Verbose -Message "TLD file needs to be replaced (Days: $Days)"
	$GetNewFile = $True
	$LoadExistingFile = $False
	}
	Else {
	Write-Verbose -Message 'TLD file does not need to be replaced'
	$LoadExistingFile = $True
	$GetNewFile = $False
	}

	} ElseIf ($InternetConnection -eq $True) {
	Write-Verbose -Message 'TLD file needs to be replaced'
	$GetNewFile = $True
	} Else {
	$TLDList = $NULL
	}

	##### Get New File or Load Existing TLD File
	If ($GetNewFile) {
	try {
	Write-Verbose -Message 'Downloading TLD file'
	$FileURL = 'http://data.iana.org/TLD/tlds-alpha-by-domain.txt'
	$TLDList = (Invoke-WebRequest -Uri $FileURL).Content
	Set-Content -Path $FileLocation -Value $TLDList
	$TLDList = Get-Content -Path $FileLocation \| Where-Object {$_ -notlike '#*' -and $_ -notlike ''}
	}
	catch {
	$TLDList = $NULL
	Write-Warning -Message 'Run this function with the -MoreInfo parameter.'
	}
	} ElseIf ($LoadExistingFile) {
	Write-Verbose -Message 'Loading existing TLD file'
	$TLDList = Get-Content -Path $FileLocation \| Where-Object {$_ -notlike '#*' -and $_ -notlike ''}
	} Else {
	$TLDList = $NULL
	}
	}
	} # End Begin

	Process {
	##### Check string against TLD list
	If ($WrongVersion -ne $True) {
	Write-Verbose -Message 'Checking that TLD file has entries/values'
	If ($TLDList -ne $NULL) {
	Write-Verbose -Message 'Checking string against TLD file'
	$String = ($String.Split('.')[-1]).Trim().ToLower()
	If (-not($String.Length -le 0)) {
	If ($TLDList \| Select-String "^$String$") {
	Write-Output -Verbose $True
	$OutputCode = 1
	} ElseIf (-not($TLDList \| Select-String "^$String$")) {
	Write-Output -Verbose $False
	$OutputCode = 2
	}
	} Else {
	$OutputCode = 3
	Write-Output -Verbose $False
	}
	} ElseIf ($InternetConnection -eq $False -and $TLDList -eq $NULL) {
	$OutputCode = 4
	} ElseIf (($InternetConnection -eq $True -and $TLDList -eq $NULL) -or ($TLDList -eq $NULL)) {
	$OutputCode = 5
	} Else {
	$OutputCode = 7
	}
	}

	##### Write output message (-MoreInfo parameter)
	If ($MoreInfo) {
	Write-Verbose -Message 'MoreInfo parameter specified'
	switch ($OutputCode) {
	1 {Write-Output -Verbose "SUCCESS: $String`r`nMESSAGE: This TLD matches the TLD file from IANA."}
	2 {Write-Output -Verbose "FAILURE: $String`r`nMESSAGE: This TLD does not match the TLD file from IANA."}
	3 {Write-Output -Verbose "ERROR: $String`r`nMESSAGE: A usable string has not been entered."}
	4 {Write-Output -Verbose "ERROR: $String`r`nMESSAGE: No Internet Connection and No TLD file."}
	5 {Write-Output -Verbose "ERROR: $String`r`nMESSAGE: IANA URL may have changed ($FileURL) or no access to write TLD file (Check UAC)."}
	6 {Write-Output -Verbose "ERROR: Version`r`nMESSAGE: This advanced function requires Windows PowerShell 3.0 or greater."}
	7 {Write-Output -Verbose "ERROR: $String`r`nMESSAGE: Unknown Error (Output Code: $OutputCode"}
	default {Write-Output -Verbose "ERROR: $String`r`nMESSAGE: Unknown error (Output Code: Default)."}
	}
	}

	##### Display variables' values (-ShowVars parameter)
	If ($ShowVars) {
	Write-Verbose -Message 'ShowVars parameter specified'
	Write-Output "----- Variables -----"
	"String: $String",
	"Internet Connection: $InternetConnection",
	"File Location: $FileLocation",
	"File Last Write Time: $FileInfo",
	"Days Since Download: $TimeSinceDownload day(s)"
	"Days Specified: $Days day(s)",
	"Get New File: $GetNewFile",
	"Load Existing File: $LoadExistingFile",
	"Output Code: $OutputCode"
	"Show Variables: $ShowVars"
	}
	} # End Process
	} # End Function