HelloI want to disable thefeature "Accept Messages from All Sendres" onall the mailboxes whereit is set to true.The thing which i'm not getting is the switch which i can use with -AccepMessagesFromOnly .I want to have this set to False for all but :$false does not work with this.It though happens perfectly fine with one mailbox .Help required

You need to set it to $Null instead of$False... Set-Mailbox MailboxName -AcceptMessagesOnlyFrom $Null This will remove all entries fromAcceptMessagesOnlyFrom from all mailboxes in your environment... Get-Mailbox -ResultSize Unlimited | Set-Mailbox -AcceptMessagesOnlyFrom $Null Amit Tank | MVP Exchange Server | MCITP: EMA | MCSA: M | http://ExchangeShare.WordPress.com

Thanks Amit$NULL did the trick.... :-))