PS> Install-Module -Name ExchangeOnlineManagement -RequiredVersion 2.0.5
PS> Import-Module ExchangeOnlineManagement
PS> Connect-ExchangeOnline -UserPrincipalName admin@emailAddress.com -DelegatedOrganization emailAddress.onmicrosoft.com
PS> Set-CASMailbox -Identity user@goldenminute.co.uk -SmtpClientAuthenticationDisabled $false
PS> Get-CASMailbox -Identity user@goldenminute.co.uk | Format-List SmtpClientAuthenticationDisabled