Check-EmailAddress.ps1

function Check-EmailAddress {
    [CmdletBinding()]
    [OutputType([Boolean])]
    Param(
        [Parameter(Mandatory = $true,Position = 0)
        [String]$EmailAddress
    )
    Begin {
        #nothing
    }
    Process {
        return [Boolean](Get-Recipient -Filter "emailaddresses -eq $EmailAddress" -EA 0)
    }
}