Splatting doesn't work with parameter -Filter

I have this long line I want to make easier to read:

$Mail = "stantastic@example.com"    
Get-ADUser -Server example.com:3268 -Filter {EmailAddress -eq $Mail} -Properties CN,co,Company,Department,DisplayName,SamAccountName,State,Office,EmailAddress

I read that it's nice to use splatting, so I'm trying:

$Params = @{
    Server = 'example.com:3268'
    Filter = '{ EmailAddress -eq $Mail }'
    Properties = 'CN,co,Company,Department,DisplayName,SamAccountName,State,Office,EmailAddress'
}

Get-ADUser @Params

But running this throws an error:

Get-ADUser : Error parsing query: '{ EmailAddress -eq stantastic@example.com }' Error Message: 'syntax error' at position: '1'.
At line:1 char:1
+ Get-ADUser @Params
+ ~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : ParserError: (:) [Get-ADUser], ADFilterParsingException
    + FullyQualifiedErrorId : ActiveDirectoryCmdlet:Microsoft.ActiveDirectory.Management.ADFilterParsingException,Microsoft.ActiveDirectory.Management.Commands.GetADUser

What am I missing?

Solution

You should pass a filter to the ActiveDirectory module cmdlets as a string. You're needlessly including brackets in your code:

Get-ADUser -Filter "EmailAddress -eq '$Mail'"

While you can pass a scriptblock, it's implicitly being turned into a string anyways. Additionally, you're passing your properties as a single string when it's expecting an array of string.

The correct way:

$aduserParams = @{
    Server     = 'example.com:3268'
    Filter     = "EmailAddress -eq '$Mail'"
    Properties = 'CN', 'co', 'Company', 'Department', 'DisplayName', 'SamAccountName', 'State', 'Office', 'EmailAddress'
}
Get-ADUser @aduserParams

I suggest checking Get-Help for parameter types:

Get-ADUser -Filter <string>
[-ResultPageSize <int>]
[-ResultSetSize <System.Nullable[System.Int32]>]
[-SearchBase <string>]
[-SearchScope {Base | OneLevel | Subtree}]
[-AuthType {Negotiate | Basic}]
[-Credential <PSCredential>]
[-Partition <string>]
[-Properties <string[]>]
[-Server <string>]
[<CommonParameters>]