exchange 2007. If a light client, using forms-based authentication, creates a new message and the sessions times out, the browser reports: The custom error module does not recognize this error. The work around is to open a new tab, login back in, return to the error tab and refresh. It then saves a draft. Can't find any information in any logs on client or server. The error is not a lot to go on.

Hi,What do you mean light client? Outlook Web Access Light or Outlook Web Access Premium?If we use owa in light mode, Outlook Web Access Light will monitor user activity so that Outlook Web Access does not time out while a user is composing a long entry.So please ensure that you have the latest(SP2+rollup1) update installed for Exchange 2007.Regards,Xiu