Hi,

I have a user who is currently abroad. He's using either RPC/HTTPS or a MS
VPN to connect to his Exchange mailbox.
When he replies to an email he gets the following message:

From: System Administrator
Sent: Monday, March 12, 2007 5:55 PM
Subject: Undeliverable: Options
Your message did not reach some or all of the intended recipients.
     Subject:  RE: Options
     Sent:     3/12/2007 5:54 PM
The following recipient(s) could not be reached:
     XXXXX on 3/12/2007 5:55 PM
           This message could not be sent. Try sending the message again
later, or contact your network administrator. The client operation failed.
Error is [0x80004005-0x0004b9-0x000501].

The email he tried to reply to was internal to the company. He then sent it
again and it went through. This only started happening last week, and is very
random. i.e. it doesn't happen all the time.

Any help would be appreciated.

Thanks,

Bart