Exchange system has a lot of Mail Contacts - (items listed under Recipient Configuration -> Mail Contact in EMC). Don't ask me why but many of these "contacts" have the same email domain as regular mailbox users - IE normail mailbox user is user1@contoso.com and there are contacts that are user2@contoso.com, user3@contoso.com - etc. So we are getting a 4001 alert by Exchange Availability because it is trying to look up free/busy information on these contoso.com addresses but fails because they are "contacts" and there is no actual mailbox. Is there a way to keep the availability service from attempting to look up free/busy info on these accounts?

Please paste the exact error that you get in the Event Log Thanks Syed MM - Messaging SME - IBM || MCTS: Microsoft Exchange Server 2007/2010 || MCSE || MCSA ||

You need to delete the duplicate addresses from the contacts, or the entire contact. An e-mail address should only be used on one object in the entire forest. Contact can be used to allow F\B look up in another Exchange org and I'm pretty sure there is no way to prevent Exchange from referring to contacts due to this support. I have a VBScript here that will find all duplicate addresses within a forest: http://izzy.org/scripts/Exchange/Admin/Get-AddressDuplicates.vbsIf this post helps to resolve your issue, please click the "Propose as Answer" If you find it helpful , mark it as helpful by clicking on "Vote as Helpful" button at the top of this message. By marking a post as Answered, or Helpful you help others find the answer faster. If you need an expert migration consultant to assist your organization feel free to contact me directly. Jason Sherry | Blog | Hire Me | Twitter: @JasonSherry Microsoft Infrastructure Architect, MCSE: M, MCTIP, Microsoft Exchange MVP