HI,

We have Exchange 2010 with Sp1. Since last few days OOF is not working for External client. It was working earlier.

I have tested

1.

When I browse to EMC > Org. Configuration > Hub Transport > Remote Domains > Default (Properties)

"Allow external out-of-office messages and legacy out-of-office messages (configured by using Outlook 2003 or earlier clients, or configured on Exchange 2003 mailboxes)" is checked.

Under "Message Format", "Allow automatic replies" and "Allow automatic forward" are both checked.

2. I have disabled Anti virus on server

Kindly Advise.

Option which mentioned above is not related to the OOF issue..

OOF working for Internal Users? External Client in the sense are they connecting via Outlook Anywhere?

Hello,

From the description, the OOF settings is ok.

If you use outlook 2007 or outlook 2010, I recommend you use test e-mail autoconfiguration to check if there is any error for autodiscover.

Hold down the CTRL key, right-click the outlook icon in the system tray and click test e-mail autoconfiguration

And please use get-autodiscovervirtualdirectory to check your autodiscover settings, and use get-webservicesvirtualdirectory to check ews settings.

Are the external url's correct?
Do you have problems for freebusy too for external users?

+ See :
http://social.technet.microsoft.com/Forums/exchange/en-US/c765605d-27a7-4784-993c-925394e2e09f/outlook-2007-using-exchange-2007-free-busy-does-not-show

other exchange version but the cause might be the same